Taxa considered threatened by extinction are listed in ANNEX I, and trade with plants or parts thereof is strictly prohibited, for example, "Brazilian rosewood" (Dalbergia nigra, Papilionaceae).
Taxa considered overexploited but not in immediate danger of extinction may be traded in limited amounts. These are listed in ANNEX II, and trade with plants or parts thereof is subject to strict export and import controls (monitoring), for instance, "kokrodua" (Pericopsis elata, Papilionaceae; "lignum vitae" (Guaiacum officinale and G. sanctum, Zygophyllaceae).
ANNEX III contains taxa which have been put under limited protection (level as in ANNEX II) by individual countries, for instance, "true mahogany" (Swietenia macrophylla, Meliaceae) in Costa Rica.
Growth ring boundaries indistinct or absent = growth rings vague and marked by more or less gradual structural changes at their poorly defined boundary, or not visible.
Growth ring boundaries can be marked by one or more of the following structural changes:
a. Thick-walled and radially flattened latewood fibres or tracheids versus thin-walled earlywood fibres or tracheids, e.g. Weinmannia trichosperma (Cunoniaceae), Laurus nobilis (Lauraceae).
b. Marked difference in vessel diameter between latewood and earlywood of the following ring as in semi-ring-porous woods, e.g., Juglans regia (Juglandaceae), Ulmus procera (Ulmaceae).
c. Marginal parenchyma (terminal or initial), e.g. Xylopia nitida (Anonaceae), Brachystegia laurentii (Caesalpiniaceae), Juglans regia (Juglandaceae), Liriodendron tulipifera (Magnoliaceae). Irregularly zonate, tangential parenchyma bands without associated abrupt changes in fibre diameter or wall thickness are not considered marginal and do not represent distinct growth ring boundaries , e.g. Eschweilera subglandulosa (Lecythidaceae), Irvingia excelsa (Simaroubaceae).
d. Vascular tracheids and very narrow vessel elements very numerous or forming the ground tissue of the latewood, and absent from the earlywood, e.g. Sambucus nigra (Caprifoliaceae).
e. Decreasing frequency of parenchyma bands towards the latewood resulting in distinct fibre zones, e.g. Lecythis pisonis (Lecythidaceae), Donella pruniformis (Sapotaceae).
f. Distended rays, e.g. Fagus spp. (Fagaceae).
See Carlquist (1980, 1988) for other types of growth ring boundaries and for commonly occurring combinations of several of the above features.
COMMENTS
Although absence of growth ring boundaries is a clear enough descriptor, the differences between 'indistinct' and 'distinct' boundaries are somewhat arbitrary, and there are intermediates. Growth rings may appear distinct when observed macroscopically, yet have indistinct boundaries at the light microscopic level; distinctness of the ring boundaries should be judged with a microscope. Indistinct growth ring boundaries are very common in tropical trees, e.g. Spondias mombin (Anacardiaceae), Parkia nitida (Mimosaceae), Coelocaryon preussii (Myristicaceae), Xanthophyllum philippinense (Polygalaceae).
Nonperiodical, sporadic occurrence of ring boundaries (due to unusual climatic extremes or traumatic events) should be recorded as rings absent or boundaries indistinct.
COMMENTS
The variety of colours, shades, and combinations of heartwood colour make it impossible to categorise all of them. In general, the colour of heartwood is either brown, red, yellow, white, or some shade or combination of these colours. Basically brown heartwood is very common; basically red and basically yellow are rather rare; basically white or grey is rather frequent.
The heartwood colour of many taxa is not restricted to one colour, but to a combination of colours and, when appropriate, various combinations should be recorded and may be used when identifying an unknown.
Examples of these combinations include: reddish-brown in Astronium spp. (Anacardiaceae), Hymenaea spp. (Caesalpiniaceae), Quercus rubra, Fagus spp. (Fagaceae), Khaya spp., Swietenia spp. (Meliaceae); yellow and brown in Distemonanthus spp. (Caesalpiniaceae), Chlorophora tinctoria (Moraceae), Adina cordifolia (Rubiaceae), Fagara spp. (Rutaceae), Mastichodendron spp. (Sapotaceae).
Very light coloured woods would be recorded as combinations of white to grey and brown and/or yellow, e.g. Acer spp. (Aceraceae), Alstonia spp. (Apocynaceae), Anisoptera spp. (Dipterocarpaceae), Gmelina spp. (Verbenaceae).
Rare colours such as black, green, orange or purple may be used alone (e.g., as for Diospyros ebenum - Ebenaceae, which has a distinctly black heartwood), but more commonly they will be used in combination with other heartwood colours. For example, the combination of basically brown and green occurs in Bucida buceras (Combretaceae), Ocotea rodiei (= Chlorocardium rodiei, Lauraceae), Liriodendron tulipifera, Michelia spp., Talauma spp. (Magnoliaceae); the combination of basically red, brown, yellow, and orange with streaks occurs in Centrolobium spp. (Papilionaceae) and Aspidosperma spp. (Apocynaceae); the combination of brown, red, purple, black and orange with streaks occurs in Dalbergia spp. (Papilionaceae).
CAUTIONS
Do not use heartwood colour features for ancient samples, archaeological material, or other samples whose colour has been altered by burial, time, treatment, or decay.
Be particularly careful when using the feature 'Heartwood basically white to grey', because a whitish coloured sample may represent sapwood and not heartwood.
In dried wood samples the chemicals responsible for the odour may have volatised from the surface, so it will be necessary to expose a fresh surface, or take other measures to enhance the odour, e.g., add moisture by breathing on the wood, or wet the wood with water and warm it.
CAUTION
Odour is quite variable, and individual perceptions of odour often differ. Therefore, use this feature with caution and only in the positive sense.
COMMENTS
Taste is deliberately excluded from the feature list baches of safety considerations, particularly a concern that someone may try tasting a wood whose contents could cause a severe allergic reaction.
COMMENTS
Density is the weight of a substance (mass) per unit volume; specific gravity (s.g.) is the ratio of the density of a material to the density of water and, consequently, specific gravity does not have units. For purposes of computing specific gravity of wood, wood density uses the oven-dry weight as the numerator. Because the volume of wood changes with changes in moisture content below fibre saturation point, it is necessary to specify the moisture content at which specific gravity is determined. Basic specific gravity (Bsg), which is based on the green volume (wood fully swollen, moisture content of fibre saturation point or higher) is one of the most commonly cited values (Panshin & DeZeeuw 1980).
Other values often given for wood include basic density (Bd) which is equal to the oven-dry weight of wood/green volume and which has units (g/cm3, kg/m3, or lbs/ft3). To convert from basic specific gravity (Bsg) to basic density (Bd) multiply the basic s.g. by the density of water as is shown below:
Bd in g/cm3 = Bsg x 1 g/cm3
Bd in kg/m3 = Bsg x 1000 kg/m3
Bd in lbs/ft3 = Bsg x 62.4 lbs/ft3. Therefore
Bsg of 0.4 = Bd 0f 0.4 g/cm3, 400 kg/m3, or 25 lbs/ft3
Bsg 0f 0.75 = Bd of 0.75 g/cm3, 750 kg/m3, or 46.8 lbs/ft3.
COMMENTS
Vesselless dicotyledonous woods are relatively uncommon and are distinguished from coniferous wood by tall multiseriate rays. For vesselless woods, it is necessary to code for type of imperforate tracheary elements (fibres or vascular/vasicentric tracheids) and impossible to code for vessel features (see specifications file).
Wood semi-ring-porous = 1) wood in which the vessels in the earlywood are distinctly larger than those in the latewood of the previous growth ring, but in which there is a gradual change to narrower vessels in the intermediate and latewood of the same growth ring;
or 2) wood with a distinct ring of closely spaced earlywood vessels that are not markedly larger than the latewood vessels of the preceding ring or the same growth ring. Alternative definition. intermediate condition between ring-porous and diffuse-porous wood, e.g., Cordia trichotoma (Boraginaceae), Juglans nigra (Juglandaceae), Lagerstroemia floribunda (Lythraceae), Cedrela odorata (Meliaceae), Pterocarpus indicus (Papilionaceae), Prunus amygdalus (Rosaceae), Paulownia tomentosa (Scrophulariaceae).
Wood diffuse-porous = wood in which the vessels have more or less the same diameter throughout the growth ring, e.g., Acer spp. (Aceraceae), Rhododendron wadanum (Ericaceae), Cercidiphyllum japonicum (Cercidiphyllaceae), Swietenia spp. (Meliaceae), Enterolobium spp. (Mimosaceae); the vast majority of tropical species and most temperate species.
COMMENTS
The three features for porosity form an intergrading continuum and many species range from diffuse-porous to semi-ring-porous, or from ring-porous to semi-ring-porous. Porosity is coded independently of vessel arrangement. This implies that woods with a distinct vessel arrangement (character states 1 or 2 or 3), as well as those with evenly distributed vessels, may be diffuse-porous.
In some temperate diffuse-porous woods (e.g., Fagus spp. - Fagaceae, Platanus spp. - Platanaceae) the latest formed vessels in the latewood may be considerably smaller than those of the earlywood of the next ring, but vessel diameter is more or less uniform throughout most of the ring.
In a description, characteristics of the earlywood ring of ring-porous woods should be noted, i.e., describe how many vessels wide the ring is. Sudo's (1959) key used the features 'pore ring: 1-seriate' and 'pore ring: multiseriate'. Such characteristics can be useful in distinguishing between species, e.g., Ulmus americana typically has an earlywood zone that is one vessel deep, Ulmus rubra has an earlywood zone that is more than two vessels deep.
CAUTION
Slow-grown ring-porous woods have narrow growth rings with very little latewood. Be careful not to confuse the closely spaced earlywood zones of slow-grown ring-porous woods with a tangential pattern, or to interpret such woods as diffuse-porous.
Vessels in diagonal and/or radial pattern = vessels arranged radially or intermediate between tangential and radial (i.e., oblique), e.g., Lithocarpus edulis (Fagaceae), Calophyllum brasiliense, C. papuanum, Mesua ferrea (Guttiferae), Eucalyptus diversicolor, E. obliqua (Myrtaceae), Amyris sylvatica (Rutaceae), Chloroluma gonocarpa (Sapotaceae). Synonym for diagonal: 'in echelon'.
Vessels in dendritic pattern = vessels arranged in a branching pattern, forming distinct tracts, separated by areas devoid of vessels, e.g., Rhus aromatica (Anacardiaceae), Castanea dentata (Fagaceae), Chionanthus retusus (Oleaceae), Rhamnus cathartica (Rhamnaceae), Bumelia lanuginosa (Sapotaceae). Synonym: 'flame-like'.
'No specific pattern' (feature 18,4) has been added as a term of convenience for use with DELTA and, since the majority of hardwoods does not feature specific vessel patterns, usually constitutes the 'implicit' value.
PROCEDURE
Vessel distribution patterns (tangential, diagonal/radial, dendritic) are determined from the cross section at a low magnification, and are recorded only where there is a distinct pattern. In ring-porous woods, only the intermediate and latewood are examined. The ring of vessels at the beginning of the growth ring of ring-porous woods is not considered when determining vessel distribution patterns.
COMMENTS
These features often occur in combination. Vessel arrangement in some woods intergrades between tangential and diagonal. Diagonal and dendritic often intergrade. All applicable features should be recorded.
The arrangement of pore clusters seen in most species of Ulmus (Ulmaceae) has been called 'ulmiform'; this describes woods where the latewood clusters are predominantly in wavy tangential bands (character state 1), and sometimes tend to a diagonal pattern (character state 2). Tangential arcs of vessels, typical of the Proteaceae, have been called 'festooned'.
Since, in ring-porous temperate species, these patterns (character states 1–3) may be restricted to the latewood, their expression depends on growth ring width, and when rings are narrow these patterns are not obvious.
CAUTION
Care is needed to recognise the following as not being multiples: (i) solitary vessels composed of vessel elements with oblique overlapping end walls giving the appearance of vessel pairs on the cross section as in Cercidiphyllum (Cercidiphyllaceae) and Illicium (Illiciaceae), and (ii) closely associated solitary vessels, as in some species of Eucalyptus (Myrtaceae) and Calophyllum (Guttiferae) (Brazier & Franklin 1961).
Clusters common = groups of 3 or more vessels having both radial and tangential contacts, and of common occurrence, e.g., Polyscias elegans (Araliaceae), Pittosporum ferrugineum (Pittosporaceae), latewood of Gleditsia triacanthos, Gymnocladus dioica (Caesalpiniaceae), Morus alba (Moraceae), and Ailanthus altissima (Simaroubaceae).
Short radial multiples of 2–3 vessels in combination with a variable number of solitary vessels is the most common form of vessel grouping.
COMMENTS
State 2 'radial multiples of 4 or more common' should be used only when radial multiples of 4 or more are an obvious feature of the transverse section. State 3 'clusters common' applies only when clusters are frequent enough that they are easily observed during a quick scan of a cross section. Clusters and radial multiples of 4 or more are not mutually exclusive and can occur in combination. Woods with vessels in tangential bands often have clusters.
When describing a wood, an index of vessel grouping can be calculated in the manner recommended by Carlquist (1988): count the total number of vessels in a minimum of 25 vessels 'groups' (i.e., count both solitary vessels and vessel multiples as a 'group'), divide the total number of vessels by 25 (the number of groups counted). An index of 1.00 indicates exclusively solitary vessels, and the higher the index, the greater the degree of vessel grouping.
PROCEDURE
In ring-porous woods, examine the latewood because in these woods the earlywood vessels are almost always circular to oval in outline. Use the outline of solitary vessels only because the common walls of vessels in multiples can be flattened giving part of the vessels an angular outline.
CAUTION
For fossil and archaeological samples, use this feature only when there obviously is no distortion from shrinkage or post-depositional events. Distortion and 'folding' of the rays indicates that the wood has been compressed during burial and that vessel outline probably has been altered.
COMMENT
Vines and xerophytes often have two distinct vessel diameter classes (Carlquist 1985); Baas & Schweingruber 1987).
Vessel diameter is measured in transverse sections. Vessels are selected for measurement with care not to bias the selection towards the larger or smaller vessels. The tangential diameter of the vessel lumina, excluding the wall, is measured at the widest part of the opening. At least 25 vessels should be measured.
In ring-porous woods and woods with 'two distinct vessel diameter classes' present only measure and record the larger size class. Information about tangential diameters of the smaller vessels would be useful in a description.
In semi-ring-porous woods, measure along a radial transect through a growth ring. For semi-ring-porous woods, it is recommended that more than 25 vessels be measured; a larger standard deviation is expected for such woods.
It is recommended to enter a range of values, e.g., 70 – 100 µm.
COMMENT
In trees, mean tangential diameter of 100–200 µm are more common than mean tangential diameters greater than 200 µm or mean tangential diameters less than 50 µm. In shrubs, mean tangential diameters of less than 50 µm are common.
All vessels are counted as individuals, e.g., a radial multiple of 4 would be counted as four vessels (Wheeler 1986). Count all the vessels in at least five (and preferably ten) fields of appropriate size (depending on vessel diameter and distribution), and convert to number per square millimetre, i.e., for woods with small diameter vessels use fields 1mm x 1mm or less; for woods with large vessels that are widely spaced use whole fields of view at low magnification (e.g., 4 x objective lens). Of the vessels that are partially in the field of view, only 50% are included in the count. If vessel frequency is very low, examine enough fields to account for local variations, and preferably count at least 100 vessels.
It is recommended to enter a range of values, e.g., 18–28 vessels per square millimetre.
COMMENT
Vessel frequency is not computed for ring-porous woods, or for woods with their vessels in definite tracts with vascular/vasicentric tracheids, e.g., dendritic patterns as seen in Rhamnus cathartica (Rhamnaceae), or tangential bands as seen in Ulmus (Ulmaceae).
Measure the whole length of each vessel element from one tail end to the other, preferably in maceration. At least 25 vessel elements are measured to derive the mean and range.
It is recommended to enter a range of values, e.g., 350–680 µm.
Scalariform perforation plate = a perforation plate with elongated and parallel openings separated by one to many mainly unbranched bars,
e.g., Corylus avellana (Corylaceae), Goupia spp. (Goupiaceae), Liriodendron tulipifera (Magnoliaceae), Coula edulis (Olacaceae), Rhizophora mangle (Rhizophoraceae) usually with 3/4 10 bars;
e.g., Betula verrucosa (Betulaceae), Altingia excelsa, Liquidambar styraciflua (Hamamelidaceae), Sacoglotis gabonensis (Humiriaceae), Schima wallichii (Theaceae) with usually 10–20 bars;
e.g., Cercidiphyllum japonicum (Cercidiphyllaceae), Dicoryphe stipulacea (Hamamelidaceae), Nyssa ogeche (Nyssaceae), Staphylea pinnata (Staphyleaceae) with usually 20–40 bars;
e.g., Aextoxicon punctatum (Aextoxicaceae), Hedyosmum spp. (Chloranthaceae), Dillenia triquetra (Dilleniaceae) with usually = 40 bars.
Reticulate perforation plate = a plate with closely spaced openings separated by wall portions that are much narrower than the spaces between them, or with a profuse and irregular branching of wall portions resulting in a netlike appearance, e.g., Didymopanax morototoni (Araliaceae), Iryanthera juruensis (Myristicaceae).
Foraminate perforation plate = a plate with circular or elliptical openings like a sieve; the remaining wall portions can be thicker than in the reticular type, e.g., Oroxylum indicum (Bignoniaceae).
Other types = for instance, complex or radiate perforation plates, see comments.
PROCEDURE
Determine the type(s) of perforation plate from radial sections or macerations, preferably examine at least 25 vessel elements.
COMMENTS
Simple perforations are the most common type of perforation plate, and occur in over 80% of the world's woods (Wheeler & al. 1986). Most woods have exclusively simple perforations, some have simple perforations together with scalariform and/or other types of multiple perforation plates, and still others have exclusively scalariform perforation plates. When more than one type of perforation plate is present, all types should be recorded and may be used to identify an unknown (e.g., Didymopanax morototoni - Araliaceae, Oxydendron arboreum - Ericaceae, Fagus sylvatica - Fagaceae, and Platanus occidentalis - Platanaceae have both simple and scalariform plates). In those woods with both simple and scalariform perforation plates, the narrower vessel elements and the latewood vessel elements are more likely to have scalariform perforation plates.
Scalariform, reticulate, and foraminate plates form a continuum, and the latter two are often confused in the literature. Reticulate and foraminate plates are restricted to relatively few taxonomic groups and are combined here. Reticulate perforations frequently occur in combination with scalariform plates and are an elaboration of that type. Iryanthera (Myristicaceae), Dendropanax and Didymopanax (Araliaceae) have scalariform, reticulate, and varied intermediates plus simple perforations; Myrceugenia estrellensis (Myrtaceae) has simple and multiple plates, and the latter can be variously described as irregular-scalariform, foraminate, or even reticulate; Markhamia and Oroxylum (Bignoniaceae) have simple and foraminate plates.
Iryanthera (Myristicaceae) also has compound scalariform plates with few coarse bars with sets of fine secondary bars between them, which are often branched. Similar examples occur in Didymopanax morototoni (Araliaceae) and Ternstroemia serrata (Theaceae). In all these cases, both states, 2 and 3, apply. As pointed out by Carlquist (1988), the term 'ephedroid' should not be used for foraminate perforations in dicotyledons.
Radiate perforation plates (code under state 3, give additional comments under the corresponding text character) with a central wall and radiating simple and branched bars extending to the lateral vessel wall are found in Cytharexylum myrianthum (Verbenaceae) (Vidal Gomes & al. 1989) and Caryocar microcarpum (Caryocaraceae). Other types of multiple perforations may be found in future and should be recorded as feature under state3 with appropriate description under the corresponding text character.
Opposite intervessel pits = intervessel pits arranged in short to long horizontal rows, i.e., rows orientated transversely across the length of the vessel, e.g., Liriodendron tulipifera (Magnoliaceae), Nyssa ogeche (Nyssaceae).
Alternate intervessel pits = intervessel pits arranged in diagonal rows, e.g., Aceraceae, Mappia racemosa (Icacinaceae), Leguminosae, Meliaceae, Salix spp. (Salicaceae), Sapindaceae.
PROCEDURE
Generally, surface views of intervessel pits are easiest to find in tangential sections because radial multiples are the most frequent type of vessel multiple, and so intervessel pits are most frequent in tangential walls. When vessels are in tangential bands and/or clusters, radial sections also provide surface views of intervessel pits. In woods with (almost) exclusively solitary vessels, intervessel pits will be extremely rare, and often not visible in a single longitudinal section. In such woods, intervessel pit shape and size must be observed in overlapping end wall portions of vessel elements in a single vessel. However, in woods with vessel multiples, the pit arrangement, shape, and size is best determined from the middle of the larger vessel elements.
COMMENTS
Alternate intervessel pitting is the most common, and opposite and scalariform intervessel pitting are found regularly in relatively few groups. When alternate pits are crowded the outlines of the pits tend to be polygonal in surface view; if alternate pits are not crowded then the outlines of the borders are usually circular to oval. When opposite intervessel pits are crowded the outlines of the borders tend to be rectangular in surface view. Some species have both polygonal and circular to oval intervessel pit outlines (record under the corresponding text character). Combinations of different pitting patterns and/or intergrading types occur (e.g., alternate and opposite in Buxus - Buxaceae, opposite and scalariform in Liquidambar - Hamamelidaceae) and may be indicated by using combinations of the different pit features.
Measure ten pits, avoiding exceptionally large or small pits, and record the corresponding range of pit diameter.
The most widely used convention for determining pit size is to measure horizontal pit diameter. However, vertical diameter is a more constant and therefore a better diagnostic feature. To enable use of existing data (horizontal diameter) it is recommended that this dimension be recorded in a respective comment.
COMMENTS
Pit size can help distinguish between genera within a family and between families, e.g., many Meliaceae have minute pits, while many members of the Anacardiaceae have large pits.
CAUTION
Most values of pit size cited in the literature are based on horizontal pit diameter.
Do not mistake vessel-vasicentric tracheid pitting for intervessel pitting.
PROCEDURE
Vestured pits are best viewed in water or glycerin mounts (or SEM). Bleaching is recommended so as to remove encrusting materials that may be mistaken for vestures , i.e. soak sections (or, for SEM observations, wood blocks) in any household bleach until section or surface has lost its colour, rinse in water, and finish sample preparation.
When intervessel pits are relatively large and the vestures are coarse (e.g., Terminalia spp. - Combretaceae), vestures are relatively easy to see with an oil-immersion objective of a good compound microscope. But when vestured pits are minute (4 µm or less) as in the Apocynaceae or Rubiaceae, the vestures are difficult to see with a compound microscope, and only clearly visible with a scanning electron microscope.
COMMENTS
Vesturing may occur in intervessel, vessel-ray or vessel-axial parenchyma, intratracheid, or interfibre pits.
Vestures generally are characteristic of entire families, or groups within a family. The number, size, and distribution of vestures varies considerably and these variations may be of diagnostic value (Bailey 1933; Ohtani & al. 1984; Van Vliet 1978; Van Vliet & Baas 1984).
Vessel-ray pits with distinct borders, e.g., in Aceraceae, Leguminosae, Meliaceae, Ilex aquifolium (Aquifoliaceae), Betula spp. (Betulaceae), Camptostemon philippinense (Bombacaceae), Couratari oblongifolia (Lecythidaceae).
Vessel-ray pits with much reduced borders or apparently simple, e.g., in Elaeocarpus calomala (Elaeocarpaceae), Clinostemon spp. (Lauraceae), Eucalyptus spp. (Myrtaceae), Populus spp. (Salicaceae).
COMMENTS
Various combinations of vessel-ray pit features may occur and should be recorded. Vessel-ray pits in the body of the ray may differ from those in the ray margins (e.g., Palaquium galactoxylum - Sapotaceae). Record the features for both types of pits.
Vessel-axial parenchyma pitting usually resembles vessel-ray parenchyma pitting, and is therefore not included as a separate list of almost identical descriptors. Specific observations of vessel-axial parenchyma pitting should be recorded under the corresponding text character (comments).
If a wood has predominantly solitary vessels, comparison of vessel-ray pits with intervessel pits often is not possible.
Cross-field pits circular or angular, for example in Elaeocarpus calomala (ELAEOCARPACEAE), Clinostemon mahuba (LAURACEAE), Eucalyptus spp. (MYRTACEAE), Populus spp. (SALICACEAE).
Pits extended horizontally ('gash-like') and/or vertically ('palisade'), for example in Trigonobalanus verticillata, Quercus spp. (FAGACEAE), Atherosperma moschata, Laurelia aromatica (MONIMIACEAE), Horsfieldia subglobosa (MYRISTICACEAE), Syzygium spp. (MYRTACEAE).
CAUTION
For coding state 2 it is essential that truly distinct size classes or pit types be present in the vessel-ray crossfields.
Vessel-ray pits unilaterally compound and coarse (over 10 µm), e.g., in Michelia champaca (Magnoliaceae), Ceriops spp., Kandelia spp., Rhizophora spp. (Rhizophoraceae).
COMMENTS
Helical thickenings are rather variable in terms of thickness (fine to coarse), inclination angle (nearly horizontal to steeply inclined), branching (branched or unbranched), and spacing (close to wide).
Helical thickenings can also occur in vascular/vasicentric tracheids, and in ground tissue fibres, and very rarely in axial parenchyma.
CAUTION
Do not confuse coalescent pit apertures with helical thickenings!
Helical thickenings only in vessel element tails, e.g., in Cercidiphyllum japonicum (Cercidiphyllaceae), Liquidamber styraciflua (Hamamelidaceae), Schima wallichii (Theaceae).
PROCEDURE
In ring-porous woods, it is best to examine the earlywood vessels for tyloses because tyloses are often absent from small diameter latewood vessels. Avoid sapwood when determining the presence of tyloses (or gums).
COMMENTS
Tyloses may be few or many, ranging from all vessels filled with many tyloses to a few vessels with a few tyloses. This feature applies only when tyloses are not of sporadic occurrence. Tyloses may be thin-walled or thick- walled, pitted or unpitted, with or without starch, crystals, resins, gums, etc. Such information should be recorded as comment.
CAUTION
Absence of tyloses is not diagnostic; for identification feature 49 can be used only in the positive sense.
Do not code traumatic tyloses such as occur in wound heartwood, and be careful not to confuse tyloses with foamy deposits, masses of fungi, or other deposits.
COMMENTS
Woods with sclerotic tyloses usually have thin-walled tyloses as well, and both character states may apply. Some woods may have both tyloses and gum deposits (see following character).
In cross sections, deposits appear to completely fill some vessel lumina; in longitudinal sections, deposits often appear to collect at the end of vessel elements. Deposits often can be seen more clearly by examining the woods with a hand lens; sectioning and mounting techniques may remove some of the deposits.
The feature 'other deposits' includes a wide variety of organic and inorganic chemical compounds, which are variously coloured (white, yellow, red, brown, black). In a description it is appropriate to indicate their abundance and colour as well as their chemical nature. Such information may be documented as comment. See Hillis (1987) for more information on the chemistry of deposits.
CAUTION
Use this feature positively only. Do not confuse masses of whitish fungi, which may be packed in a vessel cavity, or sclerotic tyloses with deposits.
Vasicentric tracheids = imperforate cells with numerous distinctly bordered pits in their radial and tangential walls, present around the vessels, and different from ground tissue fibres, often, but not always of irregular shape, e.g., Castanea spp., Quercus spp. (Fagaceae), many Shorea (Dipterocarpaceae) and Eucalyptus (Myrtaceae) species.
COMMENTS
Vascular tracheids often occur in association with extensive vessel multiples or clusters, especially in the latewood. A very thorough search of macerations will reveal their presence in many species. However, for wood identification purposes use them only when they are commonly present (state 1).
The intergradation of vascular tracheids with narrow vessel elements implies that there are some cells with a single, often very small, perforation. Some anatomists would prefer to call such cells vascular tracheids, others would prefer to call them narrow vessel elements, probably terminating a vessel. Because they have a perforation such cells are best referred to as vessel elements; tracheids are imperforate cells.
The IAWA glossary (1964) includes shortness and irregular form in the definition of vasicentric tracheids, but these criteria do not always apply (e.g., in Eucalyptus spp., cf. Ilic 1987). Since vascular tracheids are often intermixed with vessels (i.e., in a vasicentric position) in many taxa, they can also be considered as vasicentric tracheids.
Fibres of medium wall thickness = fibre lumina less than 3 times the double wall thickness, and distinctly open, e.g., in Ilex spp. (Aquifoliaceae), Michelia compressa (Magnoliaceae), Salix alba (Salicaceae).
Fibres very thick-walled = fibre lumina almost completely closed, e.g., in Goupia glabra (Goupiaceae), Lophira spp. (Ochnaceae), Strombosia pustulata (Olacaceae), Krugiodendron ferreum (Rhamnaceae), Rhizophora mangle (Rhizophoraceae).
COMMENTS
Measurement of the actual thickness of fibre walls usually involves an amount of work out of all proportion to the limited diagnostic value of the figure obtained. Therefore, the classes for fibre wall thickness are based on the ratio of lumen to wall thickness (Chattaway 1932). The ratio proposed is that of the width of the lumen to the combined thickness of the walls between it and the lumen of the next cell as viewed in cross section. When cells are flattened radially the lumen becomes oval and will give a different ratio with the wall according to whether it is measured radially or tangentially; the radial measurement is suggested.
Chattaway (1932) suggested four categories; three are used here. State 1 roughly corresponds to her category 'very thin-walled'; state 2 includes her two categories 'thin' and 'thick'; state 3 is identical to her category 'very thick'.
Fibre wall thickness in many species is variable and there may be more than one category of fibre wall thickness in a species.
CAUTION
In woods with distinct growth rings, fibre wall thickness changes throughout the growth ring, and may be particularly thick at the end of the growth ring. When describing fibre wall thickness, do not consider the last latewood fibres. Also, do not describe gelatinous fibres (i.e., tension wood fibres), which usually have thick walls with an unlignified gelatinous layer.
Use macerations of mature trunk wood, and measure the length of at least 25 fibres to determine the mean, range, and standard deviation.
For woods with distinct growth rings, sample from the middle of the growth ring. Because of the importance of cell length in wood quality studies, a variety of methods have been developed to insure random selection of cells for measurement. It is recommended that one of these methods be used (Dodd 1986; Hart & Swindel 1967). There are very few woods in which fibre length can be measured accurately from sections, so such a method is not recommended.
It is recommended to enter a range of values, e.g., 900–1450 µm.
Determine the nature and distribution of fibre pits only in longitudinal (radial and tangential) sections, because in cross section many fibre walls are not strictly radial or tangential. Both longitudinal and cross sections are suitable to determine if the pits are bordered or (almost) simple.
Fibre pits distinctly bordered = fibres (or fibre-tracheids or ground tissue tracheids) with bordered pits with chambers over 3 µm in diameter, e.g., Ilex spp. (Aquifoliaceae), Dillenia spp. (Dilleniaceae), Illicium spp. (Illiciaceae), Xanthophyllum spp. (Polygalaceae), Camellia spp. (Theaceae).
COMMENTS
The feature 'fibre pits distinctly bordered' partly overlaps with the descriptors 'tracheids' sensu Bailey (1936) and Carlquist (1986a, 1986b, 1988) and 'fibre-tracheids' sensu Baas (1986). It usually coincides with the feature 'fibre pits common in both radial and tangential walls'.
The following combinations are of very sporadic occurrence: 1) 'fibre pits simple to minutely bordered', i.e., pit chambers less than three µm or pits simple, in combination with pits 'common in in both radial and tangential walls', e.g., Capparis spinosa (Capparidaceae), Nyctanthes arbor-tristis (Oleaceae), Vitis vinifera (Vitaceae); 2) fibre pits 'distinctly bordered' in combination with fibre pits 'mainly restricted to radial walls', e.g., in Elaeagnus angustifolia (Elaeagnaceae).
Two types of fibres with respect to wall pitting (both 'simple to minutely bordered' and 'distinctly bordered') may occur (e.g., in some species of Vaccinium - Ericaceae).
Fibres with simple to minutely bordered pits, mainly confined to the radial walls are libriform fibres in the definition of Baas (1986) or libriform fibres and/or fibre-tracheids in the definition of Carlquist (1986a, 1986b, 1988).
The terms libriform fibres, fibre-tracheids, and 'true fibres' have been deliberately avoided as descriptors in this list because there is no consensus on their definitions.
COMMENTS
Fibres with helical thickenings usually occur in woods that also have helical thickenings in the vessel elements. However, the opposite is not true, i.e., many species with helical thickenings in their vessel elements do not have helical thickenings in the ground tissue fibres.
Helical thickenings are much more common in fibres with distinctly bordered pits than in fibres with simple or minutely bordered pits.
They also occur more frequently in temperate woods than in tropical woods.
Septa are formed after the secondary fibre walls have been deposited; they therefore do not extend to the compound middle lamellae between adjacent fibres. Septa are usually unlignified and very thin (cf. Parameswaran & Liese 1969).
COMMENTS
In some woods, all fibres are septate (state 1), e.g., Lannea welwitschii, Spondias mombin (Anacardiaceae), Canarium schweinfurthii (Burseraceae). In other woods, both septate and nonseptate fibres occur together (state 2), e.g., Buchenavia capitata (Combretaceae), Elaeocarpus spp. (Elaeocarpaceae), Swietenia macrophylla (Meliaceae).
The septate fibres may then either be scattered irregularly (state 1), situated near the vessels or the rays (state 2), or arranged in tangential bands that resemble parenchyma bands (state 3). The fibres of parenchyma-like fibre bands are usually septate; the ordinary fibres they alternate with may be nonseptate as in Cassine maurocenia, Maytenus obtusifolia (Celastraceae), or septate as in Lagerstroemia tomentosa, Physocalymma scaberrimum (Lythraceae).
The number of septa per fibre can vary from one to many. This number can be taxon specific (e.g., Van Vliet 1976b), and so the average number of septa per fibre should be documented as comment for inclusion in the respective taxon description.
CAUTION
Do not confuse torn cell wall fragments, cell wall deformations, gum deposits, fungal hyphae, or tyloses in fibres (observed in some Magnoliaceae, Lauraceae, Sapotaceae) with septa.
Avoid tension wood, because gelatinous fibres are nonseptate.
COMMENT
It is necessary to study longitudinal sections in combination with transverse sections to be sure axial parenchyma is absent or extremely rare (i.e., very difficult to find; only a few strands per section). This feature may be used in combination with the features 'axial parenchyma paratracheal' and 'scanty', or with the features 'axial parenchyma apotracheal' and 'diffuse' if, despite of the scarcity of parenchyma strands, the distribution is clear.
When identifying an unknown, use the most obvious type of parenchyma pattern first and then the less evident type or types. Be sure to use a broad field of view when determining the predominant parenchyma pattern(s) from the transverse section. Various combinations of the three general types (apotracheal, paratracheal, and banded) described below may be present in a given wood.
COMMENT
This feature should be coded only when parenchyma bands constitute a distinct characteristic of the transverse section. Parenchyma bands may be mainly independent of the vessels (apotracheal), definitely associated with the vessels (paratracheal), or both. The feature 'apotracheal versus paratracheal' thus should be coded independent of presence/absence of banded parenchyma. Bands may be wavy, diagonal, straight, continuous or discontinuous (the latter often intergrading with confluent, viz 'paratracheal axial parenchyma 'confluent').
Sometimes marginal parenchyma bands are associated with axial intercellular canals (see under secretory structures).
In some temperate woods there are discontinuous bands/lines of parenchyma at the growth ring boundary; this condition also should be coded as 'marginal'.
Marginal parenchyma includes terminal and initial parenchyma, and seemingly marginal includes what has been called 'irregular zonate' bands.
Parenchyma scalariform = parenchyma in fairly regularly spaced fine lines or bands, arranged horizontally or in arcs, appreciably narrower than the rays and with them producing a ladder-like appearance in cross section. The distance between the rays is greater than the distance between parenchyma bands, e.g., Anisophyllea spp. (Anisophylleaceae), Onychopetalum spp. and most other Annonaceae, Cardwellia sublimis, Embothrium mucronatum (Proteaceae), Rhopalocarpus spp. (Rhopalocarpaceae).
Parenchyma bands much wider than rays = as per feature descriptor, e.g., Ficus spp. (Moraceae), Symphonia globulifera (Guttiferae), Lophira alata (Ochnaceae).
CAUTION
In the past, some anatomists (e.g., Record 1944) have used the term 'reticulate' for abundant diffuse-in-aggregates parenchyma with numerous short interrupted lines (features 70,1 + 71,2). This pattern does not coincide with 'reticulate' as used in the context of this list as it refers to short series of cells offset against each other, and lacking the tangential continuity of bands (interrupted only by the rays).
Parenchyma bands more than three cells wide = as per feature descriptor, e.g., Dicorynia paraensis (Caesalpiniaceae), Entandrophragma candollei (Meliaceae), Ficus retusa (Moraceae) Lophira alata (Ochnaceae), Pterygota brasiliensis (Sterculiaceae), Erisma uncinatum (Vochysiaceae).
COMMENTS
Bands over three cells wide are usually visible to the unaided eye.
For woods with marginal and reticulate or scalariform parenchyma bands, the band width also should be recorded.
It is recommended to enter a range of values, e.g., 4–9 bands per mm.
Paratracheal axial parenchyma = axial parenchyma associated with the vessels or vascular tracheids; types of paratracheal parenchyma are scanty paratracheal, vasicentric, aliform (subtypes: lozenge-aliform, winged- aliform), confluent, and unilateral paratracheal.
Axial parenchyma diffuse-in-aggregates = parenchyma strands grouped into short discontinuous tangential or oblique lines, e.g., Durio spp. (Bombacaeae), Hura crepitans (Euphorbiaceae), Ongokea gore, Strombosia pustulata (Olacaceae), Agonandra brasiliensis (Opiliaceae), Dalbergia stevensonii (Papilionaceae), Pterospermum spp. (Sterculiaceae), Tilia spp. (Tiliaceae).
COMMENTS
Because there is a continuous range from parenchyma extremely rare, diffuse, diffuse-in-aggregates, to parenchyma in narrow bands or scalariform, for some taxa it will be necessary to record more than one feature for apotracheal parenchyma. Diffuse and diffuse-in-aggregates frequently occur in combination. Record (1944) referred to diffuse-in-aggregates parenchyma as 'reticulate'. This list does not follow that usage, but uses 'reticulate' to describe a type of banded parenchyma.
CAUTION
Although by definition apotracheal parenchyma is not associated with vessels, woods with abundant diffuse and diffuse-in-aggregates parenchyma may exhibit several strands touching the vessels. Such random contacts should not be recorded as paratracheal parenchyma.
Apotracheal diffuse parenchyma sometimes occurs primarily near the rays ('ray adjacent parenchyma' of Carlquist 1988), and should not be confused with sheath cells in rays (see under rays).
Axial parenchyma vasicentric = parenchyma cells forming a complete circular to oval sheath around a solitary vessel or vessel multiple, e.g., Tachigalia myrmecophylla (Caesalpiniaceae), Octomeles sumatrana (Datiscaceae), Ocotea porosa (Lauraceae), Khaya grandifoliola (Meliaceae), Anadenanthera spp., Enterolobium cyclocarpum, Piptadeniastrum africanum (Mimosaceae), Olea europaea (Oleaceae).
Axial parenchyma aliform = parenchyma surrounding or to one side of the vessel and with lateral extensions. For subtypes and examples see under feature 73.
Axial parenchyma confluent = coalescing vasicentric or aliform parenchyma surrounding or to one side of two or more vessels, and often forming irregular bands, e.g., Kigelia africana (Bignoniaceae), Caesalpinia ferrea, Peltogyne confertiflora (Caesalpiniaceae), Marmaroxylon racemosum, Parkia pendula (Mimosaceae), Chlorophora tinctoria (Moraceae), Bowdichia nitida, Vatairea guianensis (Papilionaceae).
Axial parenchyma unilateral paratracheal = paratracheal parenchyma forming semicircular hoods or caps only on one side of the vessel and which can extend tangentially or obliquely in an aliform or confluent or banded pattern, e.g., Aspidosperma desmanthum (Apocynaceae), Caraipa grandiflora (Bonnetiaceae), Peltogyne confertiflora (Caesalpiniaceae), Mammea bongo (Guttiferae), Dilobeia thouarsii (Proteaceae).
COMMENTS
Scanty paratracheal includes what has been described in the literature as 'incomplete vasicentric'.
Some woods have vasicentric, aliform, and confluent paratracheal parenchyma. Confluent often intergrades with banded and may be recorded or used in combination with the feature 'width of parenchyma bands'.
'Unilateral paratracheal parenchyma' is used in combination with 'aliform' and/or 'confluent' when the unilateral parenchyma extends laterally or obliquely. Unilateral includes both abaxial and adaxial because generally it is not possible to distinguish between the two in a wood fragment.
Woods with several types of paratracheal parenchyma co-occurring and/or intergrading have been assigned the general descriptor 'parenchyma predominantly paratracheal' by several authors.
CAUTION
Vasicentric/vascular tracheids are often thinner-walled than ground tissue fibres, and in cross sections may be confused with axial parenchyma. Examine longitudinal sections to determine whether vasicentric/vascular tracheids or axial parenchyma surround the vessels.
Axial parenchyma winged-aliform = parenchyma surrounding or to one side of the vessel with lateral extensions being elongated and narrow, e.g., Jacaranda copaia (Bignoniaceae), Terminalia superba (Combretaceae), Brosimum spp. (Moraceae), Quassia amara (Simaroubaceae), Gonystylus spp. (Thymelaeaceae).
Parenchyma strand = a series of axial parenchyma cells formed through transverse division(s) of a single fusiform cambial initial cell, for example:
Two cells per strand, e.g., Dalbergia spp., Lonchocarpus spp., Pterocarpus spp. (Papilionaceae).
Three to four cells per strand, e.g., Terminalia spp. (Combretaceae), Ligustrum spp., Syringa spp. (Oleaceae), Nesogordonia spp. (Sterculiaceae).
Five to eight cells per strand, e.g., Nerium oleander (Apocynaceae), Macaranga spp. (Euphorbiaceae), Fraxinus spp. (Oleaceae).
Over eigth cells per strand, e.g., Bhesa spp. (Celastraceae), Lophira spp. (Ochnaceae), Minquartia spp., Tetrastylidum spp. (Olacaceae).
COMMENTS
Type of parenchyma, fusiform versus strand, is determined from tangential sections. Fusiform parenchyma cells are relatively uncommon and generally occur in woods with storied structure and short axial elements. In some species, combinations of the above features occur, e.g., fusiform cells and strands composed of two or more cells.
CAUTION
Be careful not to confuse uniseriate rays or septate fibres with strand parenchyma.
It is recommended to enter a range of values, e.g., 3–7 cells per strand.
CAUTION
Be careful not to determine the number of cells per strand from chambered crystalliferous strands.
Unlignified parenchyma usually occurs in broad bands, and is restricted to a small number of taxa, e.g., Apeiba spp., Entelea arborescens, Heliocarpus spp. (Tiliaceae), Laportea stimulans (Urticaceae).
Rayless woods, i.e. woods with only axial elements, are restricted to a small number of taxa, e.g, Arthrocnemum macrostachyum (Chenopodiaceae), Heimerliodendron brunonianum (Nyctaginaceae), Hebe salicifolia, Veronica traversii (Scrophulariaceae). See also Carlquist 1988.
CAUTION
In rayless woods with included phloem (e.g., several Chenopodiaceae), the conjunctive parenchyma (i.e., the parenchyma linking two or more phloem strands) may from radial extensions which resemble rays. In such woods there may be a continuum from short radial wedges to long radial strips to 'normal' multiseriate rays (Fahn & al. 1986), and the feature 'rays absent' should be used with caution in such woods.
The number of rays per linear unit is best determined from a tangential section along a line perpendicular to the rays' axis; it can also be determined from a cross section. Make ten measurements and record mean, range and standard deviation. It is recommended to enter a range of values, e.g., 11–18 rays per linear mm.
COMMENT
The number of rays per mm lies most often between 4 and 12 (Metcalfe & Chalk 1950); it is less frequently below 4 or above 12. The number of rays per mm cannot sensibly be determined in woods with aggregate rays, or woods with very broad rays and two distinct size classes (see corresponding ray features), e.g., Quercus spp. (Fagaceae).
Rays exclusively uniseriate, e.g., Lophopetalum beccarianum (Celastraceae), Terminalia superba (Combretaceae), Hura crepitans (Euphorbiaceae), Castanea sativa (Fagaceae), Populus spp. (Salicaceae).
PROCEDURE
Determine ray width on the tangential section.
CAUTION
The features for ray width do not apply to rays containing radial canals or to the rays composing an aggregate ray. Thus, for a wood with exclusively uniseriate rays, except for the rays with radial canals, describe the wood by recording the features referring to radial canals.
Rays commonly 3 to 5 cells wide, e.g., Swietenia macrophylla, Entandrophragma cylindricum (Meliaceae), Hymenaea courbaril (Caesalpiniaceae), Hevea brasiliensis (Euphorbiaceae), Shorea subg. rubroshorea (Dipterocarpaceae), Clarisia racemosa (Moraceae), Couratari spp. (Lecythidaceae).
Rays commonly 5 to 10 cells wide, e.g., Acer saccharum (Aceraceae), Spondias mombin (Anacardiaceae), Anisoptera laevis (Dipterocarpaceae), Khaya anthotheca (Meliaceae), Celtis sinensis (Ulmaceae).
Rays commonly more than 10 cells wide, e.g., Quercus spp. (Fagaceae), Poraqueiba guianensis (Icacinaceae), Rapanea spp. (Myrsinaceae), Platanus spp. (Platanaceae), Cardwellia sublimis, Grevillea robusta (Proteaceae), Tamarix aphylla (Tamaricaceae), Jaquinia revoluta (Theophrastaceae).
PROCEDURE
Determine ray width on the tangential section by counting the number of cells in the widest part of the rays, perpendicular to the ray axis. When rays are of two distinct size classes, record the width of the larger size class in the database.
COMMENTS
Woods with exclusively uniseriate rays and rays more than 10 cells wide are the least common.
It is recommended to enter a range of values, e.g., 3–5 cells.
CAUTION
The features for ray width do not apply to rays containing radial canals or to the rays composing an aggregate ray. Thus, for a wood with exclusively uniseriate rays, except for the rays with radial canals, describe the wood by recording the features referring to radial canals.
COMMENTS
There is variation in the size of the individual rays of aggregate rays. In some species the aggregate rays are composed of narrow rays, e.g., Carpinus spp. (Corylaceae), while in others they are composed of broad rays, e.g., Emmotum orbiculatum (Icacinaceae).
Aggregate rays occur in few taxonomic groups.
CAUTION
Aggregate rays may be relatively infrequent in the taxa in which they occur, so they may be easily overlooked or absent in a small sample; therefore, this feature should preferably be used positively only.
COMMENTS
There are no limits for the size classes - the smaller rays may be 1- or 2- or 3-seriate, the larger rays may be less than 5-seriate.
Generally, to fit the feature definition, intermediate rays should not exist between the two populations or be quite rare. Thus, when very large rays occur with few medium-sized and more numerous small rays (e.g., Fagus), this feature may still be coded 'present'.
CAUTIONS
Whether a wood has rays of two distinct widths cannot be determined from the cross section because in this view the long uniseriate wings of heterocellular multiseriate rays might be interpreted incorrectly as narrow rays.
Aggregate rays per se should not be considered a separate ray size class. Only in those species where the aggregate rays are composed of much broader rays than the nonaggregate rays does state 1 apply, e.g., several species of Casuarina (Casuarinaceae) and Quercus (Fagaceae).
Ray height over 1000 µm = the large rays commonly exceeding 1 mm in height, e.g., Guatteria schomburgkiana (Anonaceae), Anisoptera laevis (Dipterocarpaceae), Uapaca guianensis (Euphorbiaceae), Scottellia coriacea (Flacourtiaceae), Barringtonia asiatica (Lecythidaceae), Platanus occidentalis (Platanaceae), Paypayrola guianensis (Violaceae).
PROCEDURE
Determine total ray height in tangential section, along the ray axis.
COMMENT
In this list three categories for total ray height are used as opposed to the IAWA List (1989) and some of the earlier multiple entry keys (Clarke 1938; Brazier & Franklin 1961). More detailed ray height data generally are given in descriptions and may be helpful in distinguishing between taxa in some groups (recorded as comment). Ray height is quite variable in some woods (particularly woods with markedly heterocellular rays), but quite uniform in others (particularly woods with storied structure.
Use radial sections to determine the cellular composition of rays because types of ray cell (procumbent, upright, and square) are defined on the basis of their appearance in radial section.
COMMENTS
Generally, upright and square cells, if present in combination with procumbent cells, are located in the marginal rows, i.e., those rows at the top and bottom of the ray, and procumbent cells are located in the body (centre) of the ray.
The cellular composition of the multiseriate and uniseriate rays in the same wood is not necessarily the same. In some woods, their uniseriate rays are composed only of upright cells, while their multiseriate rays are composed of both upright/square and procumbent cells. In woods with uniseriate and multiseriate rays - describe the cellular composition of the multiseriate rays, not the uniseriate rays.
Some woods have more than one category of ray type with respect to cellular composition, only record the relatively common categories.
Though still employed for descriptive purposes in the character notes, the terms 'homocellular', heterocellolar', 'homogeneous' and 'heterogeneous' have been excluded from the actual feature list as there is no consensus as to their exact definition and application (e.g., to hardwoods or softwoods).
CAUTIONS
Ray composition often varies between juvenile and mature wood. In many species, rays near the pith may be composed entirely of upright cells, while rays distant from the pith are composed largely of procumbent cells with only a few rows of upright and/or square cells. When creating a database, only examine mature wood samples or, for shrubs, the peripheral wood of the thickest available stems. When an unknown wood fragment is from a thin branch, do not use ray composition for identification.
Although in tangential section, marginal rows of upright and/or square cells often will appear as uniseriate margins, the presence of uniseriate margins alone is not a reliable indicator of heterocellular rays. In some woods (e.g., Carya spp. - Juglandaceae), there are uniseriate marginal rows visible in tangential section, and these cells appear larger than the body cells, but when viewed in radial section these cells are procumbent, as are the cells of the multiseriate portion.
Sheath cells (feature 91) or tile cells (feature 92) are not considered when determining ray cellular composition.
Just the presence of sheath cells or tile cells also does not qualify a wood for coding state 2.
Body ray cells procumbent with mostly 2–4 rows of upright and/or square marginal cells, e.g., Liquidamber styraciflua (Hamamelidaceae), Carapa guianensis (Meliaceae), Treculia africana (Moraceae), Alseis peruviana (Rubiaceae), Euscaphis spp. (Staphyleaceae).
Body ray cells procumbent with over 4 rows od upright and/or square marginal cells, e.g., Weinmannia descendens (Cunoniaceae), Quintinia spp. (Escalloniaceae), Homalium foetidum (Flacourtiaceae), Humiria spp. (Humiriaceae), Ottoschulzia spp. (Icacinaceae), Coffea spp. (Rubiaceae), Turpinia spp. (Staphyleaceae).
COMMENT
Presence of sheath cells should be determined from tangential sections. There is variability in the frequency and distinctiveness of sheath cells. In some species most, if not all, multiseriate rays have sheath cells which are much larger than the other ray cells, while in others sheath cells are not frequent and/or slightly larger than the adjacent cells. When identifying an unknown wood sample, do not use this feature as a first line of approach unless it is well marked.
CAUTION
Do not confuse sheath cells with tile cells, which are always found in the body of the ray as well as the edges, and are visible in both tangential and radial sections.
COMMENTS
Tile cells sometimes have been classified into two groups: type 'Durio' when they have the same height as the procumbent ray cells, and type 'Pterospermum' when they are higher. However, this distinction is dubious because there are intergradations between the two, as in Guazuma (Sterculiaceae), and Grewia (Tiliaceae).
Tile cells do not occur in uniseriate rays, and as far as is known are restricted to the order Malvales.
COMMENTS
The type of perforation in a perforated ray cell may be simple, scalariform, reticulate, or foraminate, and does not necessarily coincide with the type of perforation plate occurring in the vessel elements of the same wood. For instance, Sloanea monosperma (Elaeocarpaceae) and Richeria racemosa (Euphorbiaceae) have simple perforations in the vessel elements and scalariform perforations in the perforated ray cells. In Siparuna (Monimiaceae) there is a range of multiple perforations in the ray cells, but the vessel element perforations are simple and/or scalariform with variations depending on species.
Perforated ray cells have bordered pits similar to the intervessel pits. They can occur individually or in radial or tangential rows. Radial rows of perforated ray cells with perforations in the tangential walls have been described as radial vessels (Van Vliet 1976a).
CAUTION
Use this feature positively only and with some caution because species that have perforated ray cells may have them in such low frequency that they could easily have been overlooked when creating a database, or examining an unknown.
COMMENT
Axial parenchyma may also be disjunctive.
PROCEDURE
The presence of storied structure should be determined from the tangential section, not the radial section!
Tiers of rays are visible at low magnification, or with the unaided eye or a hand lens, and appear as fine horizontal striations or 'ripple marks' on the tangential surface.
COMMENTS
In some woods all elements are storied, while in others various combinations of elements are storied.
There is variability within species and samples. For instance, in some samples of Swietenia (Meliaceae) rays are definitely storied, in others irregularly storied, and in still others rays are not storied.
CAUTION
Storying of wide vessel elements may be obscured because of cell enlargement during vessel development, and so it is best to examine the narrower vessel elements to determine whether vessel elements are storied.
Low rays storied, high rays nonstoried, e.g., Scaphium spp., Triplochiton scleroxylon (Sterculiaceae), Cercis canadensis (Caesalpiniaceae).
Generally, if axial parenchyma is storied, the vessel elements are also storied. However, for reasons of consistency, both tissues are maintained separately here. If axial parenchyma and vessel elements are storied, the corresponding features are recorded.
CAUTION
Storying of wide vessel elements may be obscured because of cell enlargement during vessel development, and so it is best to examine the narrower vessel elements to determine whether vessel elements are storied.
The number of ray tiers per mm can be useful in distinguishing genera and species, especially in the Leguminosae which has many taxa with storied rays.
It is recommended to enter a range of values, e.g., 4–7 tiers per mm.
Mucilage cell = a parenchymatous idioblast filled with mucilage; mostly, but not always enlarged and rounded in outline, occasionally of considerable axial extension (resembling fibres), e.g., axial in some species of Endlicheria and Ocotea (Lauraceae), and in ray parenchyma of some species of Nectandra and Persea (Lauraceae).
COMMENTS
The occurrence of oil and/or mucilage cells is limited to very few woody dicotyledons and are similar to one another except for their contents, which are easily removed during microtechnical procedures (Richter 1977).
Because it is not practical to distinguish between oil and mucilage cells by their appearance, they are listed together.
Both oil and mucilage cells are commonly associated with axial and/or ray parenchyma, but may also occur among fibres. Various combinations of these features with respect to type of contents and location occur together (see Baas & Gregory 1985; Gregory & Baas 1989, Richter 1981).
CAUTION
Traumatic canals may not occur consistently in a species, therefore, when identifying an unknown, never use the absence of traumatic canals.
Axial canals in short tangential lines = two to five axial canals in a line, e.g., Dipterocarpus spp. (Dipterocarpaceae).
Axial canals diffuse = randomly distributed solitary canals, e.g., Prioria copaifera (Caesalpiniaceae), Anisoptera spp., Cotylelobium spp., Upuna borneensis, Vateria macrocarpa, Vatica spp. (Dipterocarpaceae).
COMMENTS
It is possible to have a mixture of these features in one wood.
In some species of Dipterocarpaceae, the size of the axial canals is useful in differentiating species, i.e., whether the canals are small (diameter less than 100 µm) or large (diameter above 100 µm).
The colour of resin in canals of Dipterocarpaceae can also be useful in identification.
The effect of radial canals on ray shape (i.e., whether the canal makes the ray fusiform in shape or not), size, and number of canals per ray are also useful features.
Lacticifers = tubes containing latex, the latex may be colourless or light yellow to brown; lacticifers may extend either radially (in genera of Apocynaceae, Asclepidaceae, Campanulaceae, Caricaeae, Euphorbiaceae, Moraceae), or axially (interspersed among fibres and so far known only from Moraceae).
Tanniniferous tubes = tubes containing tannins, which are reddish-brown, in rays (so far known only from Myristicaceae).
COMMENTS
Although latex is often light-coloured, and tannins are dark, colour is not a reliable difference, and chemical tests for tannin are needed to verify the tube contents.
Structural differences between the lacticifers and tanniniferous tubes appear minor (Fujii 1988). Therefore, these two features are combined into one descriptor. Latex traces are included in this dscriptor.
Tanniniferous tubes often are difficult to recognise in tangential sections because in that view their dimensions may appear similar to the ray cells; examining radial sections shows tanniniferous tubes to be longer (indeterminate length!) than ray cells.
Included phloem, diffuse = scattered, isolated phloem strands. The phloem strands may be surrounded by parenchyma or imperforate tracheary elements, e.g., Strychnos nux-vomica (Loganiaceae). Synonym: included phloem, foraminate or island type.
COMMENTS
The feature states for included phloem type are based on the appearance of the wood, and do not have developmental inferences - they are not defined on the basis of whether there is a single permanent cambium, or successive cambia, or whether the tissue surrounding the phloem strands is xylem or conjunctive tissue. As pointed out by Mikesell & Popham (1976) and Carlquist (1988), it is desirable to restrict the term 'interxylary phloem' to those cases in which the phloem has been produced internally by a single cambium.
Included phloem of the concentric type very often intergrades with diffuse included phloem (e.g., in many Chenopodiaceae); in all cases of doubt use both feature states. In species with concentric included phloem the phloem bands may branch and anastomose, and the conjunctive parenchyma sometimes forms radial extensions resembling rays.
Because included phloem and other cambial variants are of regular occurrence in the taxa in which they are found, the term 'anomalous' must be considered a misnomer.
Other cambial variants most frequently occurs in lianas; for more information see Carlquist (1988).
The relative abundance of crystals is variable. In some species, crystals are consistently abundant; in others, they are consistently present, but not abundant; and in still other species, they are present in some samples, but absent in other samples.
Crystals, particularly the small ones, are best detected with polarised light.
CAUTION
There are many genera in which prismatic crystals are regularly absent (e.g., Dipterocarpus spp. - Dipterocarpaceae, Betula spp. - Betulaceae, Liriodendron spp. - Magnoliaceae, and Tilia spp. - Tiliaceae). But, when identifying an unknown, using absence of crystals is not recommended because crystals are of sporadic occurrence in many other taxa (e.g., Acer spp. - Aceraceae, Quercus spp. - Fagaceae, and Ulmus spp. - Ulmaceae).
Druse = a compound crystal, more or less spherical in shape, in which the many component crystals protrude from the surface giving the whole structure a star-shaped appearance, e.g., Hibiscus tiliaceus (Malvaceae). Synonym: cluster crystal.
Raphides = a bundle of long needle-like crystals, e.g., Dillenia reticulata, Tetracera boliviana (Dilleniaceae), Pisonia spp. (Nyctaginaceae), Psychotria recordiana (Rubiaceae), Tetramerista crassifolia (Tetrameristaceae), Vitis vinifera (Vitaceae).
Acicular crystals = small needle-like crystals, not occurring in bundles, e.g., Tecoma stans (Bignoniaceae), Cryptocarya glaucescens (Lauraceae), and Gmelina arborea (Verbenaceae).
Styloids = large crystals two to four times as long as broad with pointed ends, e.g., Maytenus obtusifolia (Celastraceae), Terminalia amazonica (Combretaceae), Gelsemium sempervirens (Loganiaceae), Memecylon membranifolium (Melastomataceae), Gallesia integrifolia (Phytolaccaceae), Gonystylus bancanus (Thymelaeaceae).
Elongate crystals = crystals two to four times as long as broad with pointed ends, e.g., Siphonodon pendulum (Celastraceae), Ligustrum vulgare (Oleaceae), Vitex glabrata (Verbenaceae).
Crystal sand = a granular mass composed of very small crystals, e.g., Cordia subcordata (Boraginaceae), Actinodaphne hookeri (Lauraceae), Bumelia obtusifolia (Sapotaceae), and Nicotiana cordifolia (Solanaceae). Synonym: microcrystals.
Crystals of other shapes (mostly small) = includes all other shapes of crystals, e.g., cubic (e.g., Aporusa villosa - Euphorbiaceae), navicular (boat-shaped) (e.g., Litsea reticulata - Lauraceae), spindle-shaped (e.g., Dehaasia spp. - Lauraceae), pyramidal (e.g., Caryodaphnopsis tonkinensis - Lauraceae), tabular (e.g., Aniba spp. - Lauraceae), indented (e.g., Forstiera segregata - Oleaceae), twinned (e.g., Nestegis spp. - Oleaceae), etc.
COMMENTS
Prismatic (rhomboidal) crystals are the most common type of crystal in wood (Chattaway 1955, 1956).
The other crystal types are not common, and their occurrence may be sporadic. Therefore, the respective feature states should be used only in the positive sense. Raphids and styloids often occur in enlarged cells (see corresponding feature). For more information on crystal types, see Chattaway (1955, 1956) and Richter (1980).
The difference between styloids and elongate crystals is only in size (elongated crystals are usually much smaller than styloids); therefore, these two types are summed up under one feature state (5).
CAUTION
Care must be taken not to interpret a cross section of an elongate or acicular crystal as a cubic crystal!
The crystals in raphide bundles often separate during sectioning.
In some taxa, crystals occur in only one cell type; in other taxa, they occur in more than one cell type. In the latter case, record all features that apply.
Though tyloses may not qualify as cells proper, but only as outgrowths of parenchymatous cells, the occurrence of crystals in tyloses may be of diagnostic value in some taxonomic groups. Crystals in tyloses are known to occur in many taxa, e.g., Astronium graveolens (Anacardiaceae), Cordia gharaf (Boraginaceae), Pera bumeliaefolia (Euphorbiaceae), Chlorophora tinctoria, Pseudolmedia spuria (Moraceae), Chrysophyllum auratum, and many other species of Sapotaceae.
Crystals in procumbent ray cells, e.g., Anogeissus latifolia (Combretaceae), Carpinus spp. (Corylaceae).
COMMENT
In some species, crystals occur throughout the ray. In other species with heterocellular rays they are restricted to the marginal rows of upright and/or square cells, upright and/or square cells in the body of the ray, or sheath cells. In yet others, crystals are restricted to the procumbent body ray cells. This last condition is not common and usually occurs in combination with the arrangement of 'crystals in a radial alignment'.
Crystals in chambered upright and/or square ray cells, e.g., Elaeocarpus calomala (Elaeocarpaceae), Glycidendron amazonicum (Euphorbiaceae), Banara nitida (Flacourtiaceae), Byrsonima laevigata (Malpighiaceae), Fagara flava (Rutaceae).
COMMENT
This feature may apply to crystals in nonchambered as well as chambered cells.
Crystals in nonchambered axial parenchyma cells, e.g., Ceiba spp. (Bombacaeae), Drypetes gerrardii (Euphorbiaceae), Ficus spp. (Moraceae).
COMMENT
This feature includes a considerable diversity in types of chambered or subdivided cells (cf. Parameswaran & Richter 1984), and in length of the chains of crystalliferous chambers or subdivisions. In some taxa there are only a few chambers in a series, in others there are long chains. Such information should be recorded as comment.
CAUTION
Care is needed to distinguish between crystals in septate fibres and crystals in chambered axial parenchyma cells.
COMMENT
Generally, there is only one crystal per cell or chamber. However, two or more crystals, especially acicular and/or navicular, and cubic and/or rectangular crystals, may occur in the same cell or chamber.
CAUTION
Rhaphides are bundels of crystals, but the whole bundle is considered as a single unit, and so feature state 2 (more than one crystal per cell or chamber) does not apply to raphides. Crystal sand should also not be coded under state 2.
COMMENT
It is rare that there are two distinct sizes of crystals in the same cell or chamber. This feature should be used positively only when the difference in size of crystals in the same cell or chamber is quite distinct.
COMMENT
The enlarged cells (idioblasts) can be either ray or axial parenchyma cells, or more rarely both. The crystals in enlarged cells may be prismatic crystals, druses, raphides, or any other crystal type.
COMMENT
Cystoliths, as far as is known, occur only in the examples given (Ter Welle 1980).
PROCEDURE
Silica bodies (grains and aggregates): Silica bodies are observed with the light microscope in radial sections of either permanent or temporary mounts or in cells that have been macerated. If large amounts of extractives are present and the silica bodies are difficult to see in section, bleach with a domestic bleaching agent, rinse thoroughly in water, heat in carbolic acid (this step is optional; dehydrating in alcohol often gives equally good results), and mount in clove oil, or macerate a few chips in any macerating fluid that removes most of the extractives and lignin but not the silica.
At low magnifications (4–10x objective lens), silica bodies generally appear as small dark nonbirefringent particles. At higher magnification (25–40x objective lens), they have a 'glassy' appearance.
Vitreous silica: Thoroughly macerate chips or splinters, leave the wood in the macerating solution until the wood is white. Decant the macerating fluid, add water, rinse, decant, and repeat until the solution is clear. Place some macerated wood on a slide; warm the slide on a hot plate until the macerated wood is dry. Allow the slide to cool, and then add 2 to 3 drops of concentrated sulfuric acid to dissolve the cellulose. Add a cover slip and observe the cells under a light microscope at low magnification. Vitreous silica appears like pieces of translucent vessel elements and fibres. To distinguish undissolved cells from vitreous silica use polarised light. Undissolved cells are birefringent, whereas vitreous silica is not. Vitreous silica can also be recognised in well bleached sections because of its 'glassy' appearance.
CAUTION
When looking for silica bodies or vitreous silica, do not use glycerin as a mounting medium because its refractive index makes it difficult to detect silica.
Hydrofluoric acid, which is sometimes used to soften wood, will dissolve the silica!
Silica aggregates = irregularly shaped, often comparatively large structures seemingly composed of several smaller units (grains) of silicium dioxide.
Vitreous silica = silica that coats cell walls or completely fills the cell lumina.
COMMENTS
Whether silica occurs in aggregations, as irregularly shaped or globular bodies, or whether the silica bodies have a smooth or verrucose surface may be diagnostic in certain groups and needs to be recorded in a description (use the feature for comments).
For more information on silica inclusions see Amos (1952), Ter Welle (1976), and Koeppen (1980).
Silica bodies in axial parenchyma cells, e.g., Bombax nervosum (Bombacaceae), Distemonanthus benthamianus, Apuleia leiocarpa, Dialium spp. (Caesalpiniaceae).
Silica bodies in fibres, e.g., Canarium hirsutum, Protium neglectum, Trattinickia burserifolia (Burseraceae), Ocotea splendens, Nothaphoebe kingiana (Lauraceae).
Vitreous silica in vessels and/or other cell elements, e.g., Stereospermum chelonioides (Bignoniaceae), Hydnocarpus gracilis (Flacourtiaceae), Artocarpus vriesianus (Moraceae), Gynotroches axillaris (Rhizophoraceae).
COMMENT
Silica bodies are most often restricted to ray cells, particularly the marginal or upright cells. Sometimes they are restricted to axial parenchyma; sometimes the occur in both ray and axial parenchyma. Silica bodies rarely occur in fibres, but if they do the fibres usually are septate.
PROCEDURE
Samples for testing fluorescence must be freshly surfaced; simply removing some shavings with a knife is sufficient for exposing a fresh surface. Place samples under longwave (365 nm) ultraviolet (UV) light at a distance of less than 10 cm. A high-intensity longwave UV lamp and observation in a darkened room is recommended.
COMMENTS
Fluorescent samples generally appear yellowish or greenish under the UV lamp, although some species show slight tinges of orange, pink, or violet.
Samples that are not fluorescent may reflect some of the UV light making samples appear slightly blue or purple. Some samples with a yellowish heartwood, such as Chloroxylon spp. (Rutaceae) and Gonystylus spp. (Thymelaeaceae), are not fluorescent, but may seem to have a weak yellow fluorescence because of reflection.
Absence of fluorescence can be important in some families, e.g., Anacardiaceae and Leguminosae. See Avella & al. (1989) for a survey of fluorescence in the dicotyledons.
CAUTION
This feature applies only to naturally occurring fluorescence and not to fluorescence associated with decay or pathological infections. Wood infected with decay organisms may fluoresce with streaks, spots, or a mottled appearance, e.g., wetwood of Populus tremuloides (Salicaceae) produces yellow fluorescent streaks. Naturally occurring fluorescence appears more uniform.
Oven-drying of samples or exposure to high temperatures or other extreme environmental conditions may effect fluorescence properties.
Add enough thin heartwood shavings to cover the bottom of a clean vial which is approximately 20 x 70 mm. Do not use splinters or chips, because the extraction time is much longer than for shavings. Cover shavings to a depth of approximately 20 mm (approximately 5 ml) with distilled water that is buffered at a pH of 6.86. Packets of buffering agents are available from most scientific supply companies so that only the contents of a packet need to be added to 500 or 1000 ml of distilled water to obtain the desired pH. Cover the vial and shake vigorously for 12 to 15 seconds. Allow the shavings and solution to stand for 1 to 2 minutes, and then hold the vial under a longwave (approximately 365 nm) UV lamp for extract fluorescence. Generally, extracts that fluoresce are bluish, but sometimes they are greenish.
COMMENT
Examples of woods yielding water extracts that fluoresce a brilliant blue incluse Strychnos decussata (Loganiaceae), Brosimum rubescens (Moraceae), Olea europaea subsp. africana (Oleaceae), Pterocarpus indicus (Papilionaceae), Zanthoxylum flavum (Rutaceae). Examples of wood with weaker fluorescence of water extracts, but still positive, incluse Acacia farnesiana (Mimosaceae) and Lonchocarpus capassa (Papilionaceae).
After determining the fluorescence of the water extract, place the vials on a hotplate and bring the solution to a boil. As soon as the solution boils, remove the vial and immediately determine colour.
COMMENTS
Water extract basically colourless to brown or shades of brown (feature 136,1)is the most common of the water extract feature colours.
Examples of woods with water extract basically red or shades of red (feature 136,2) include Brasilettia spp. (Caesalpiniaceae), Catha edulis (Celastraceae), Cunonia capensis (Cunoniaceae), and Mimusops caffra (Sapotaceae).
Examples of woods with water extract basically yellow or shades of yellow include Gonioma kamassi (Apocynaceae), Albizia adianthifolia, Acacia caffra (Mimosaceae).
This character was included for practical reasons, i.e., to allow a search in the database for timbers whose heartwood extractives are easily washed out when exposed to contact with running water, as for instance Intsia spp. (Caesalpiniaceae), Terminalia ivorensis (Combretaceae), Shorea subg. shorea spp. (Dipterocarpaceae). Failure to recognise, or know about this particular property of some timbers used primarily in outdoor construction may cause considerable damage, particularly in the context of increasing usage of water-based surface coatings.
Add enough thin heartwood shavings to cover the bottom of a clean vial which is approximately 20 x 70 mm. Do not use splinters or chips, because the extraction time is much longer than for shavings. Cover shavings to a depth of approximately 20 mm (approximately 5 ml) with 95% ethanol. Cover the vial and shake vigorously for 12 to 15 seconds. Allow the shavings and solution to stand for 1 to 2 minutes, and then hold the vial under a longwave (approximately 365 nm) UV lamp for extract fluorescence. Generally, extracts that fluoresce are bluish, but sometimes they are greenish.
COMMENT
Examples of woods yielding ethanol extracts with bright fluorescence include Protorhus longifolia (Anacardiaceae), Cordia gerascanthus (Boraginaceae), Acacia erioloba (Mimosaceae). Examples of wood with weaker fluorescence of ethanol extracts, but still positive, include Kiggelaria africana (Flacourtiaceae), Acacia melanoxylon (Mimosaceae), Olea capensis (Oleaceae).
Sometimes the water extract of a species fluoresces, but its ethanol extract does not (e.g., Laucaena glauca - Mimosaceae). More often, the ethanol extract fluoresces, while the water extract does not (e.g., Afzelia quanzensis - Caesalpiniaceae, Lysiloma bahamensis - Mimosaceae).
After determining the fluorescence of the ethanol extract, place the vials on a hotplate and bring the solution to a boil. As soon as the solution boils, remove the vial and immediately determine colour.
COMMENTS
Ethanol extract basically colourless to brown or shades of brown (state 1) is the most common.
Examples of woods with ethanol extract basically red or shades of red (state 2) include Rhus integrifolia (Anacardiaceae), Baikiaea plurijuga, Peltophorum dubium, Swartzia madagascariensis (Caesalpiniaceae), and Berchemia discolor (Rhamnaceae).
Examples of woods with ethanol extract basically yellow or shades of yellow (state 3) include Gonioma kamassi (Apocynaceae), Ptaeroxylon obliquum, Zanthoxylum flavum (Rutaceae), Balanites maughamii (Balanitaceae).
For more information on fluorescence and colour of water and ethanol extracts see Dyer (1988) and Quirk (1983).
PROCEDURE
Prepare a 0.5% solution of chrome azurol-S reagent by dissolving 0.5 g of the dry cheome azurol-S granules and 5.0 g of sodium acetate (buffer) in 80 ml of distilled water. After the chemicals are completely dissolved, add enough distilled water to make 100 ml of reagent. This solution is stable and can be used over a number of years. To test dry wood samples, use an eyedropper to apply one or two drops of the solution to a freshly exposed end-grain.
In highly positive woods, a bright blue color will develop in a matter of minutes, e.g., Poga spp. (Anisophylleaceae), Cardwellia spp. (Proteaceae), Symplocos spp. (Symplocaceae), all Vochysiaceae. In those woods which absorb the solution very slowly, e.g., Anisophyllea spp. (Anisophylleaceae), Goupia spp. (Goupiaceae), or contain low concentraions of aluminium, e.g., Laplacea spp. (Theaceae), Henriettea spp. (Melastomataceae), several hours may be required for the blue colour to develop.
CAUTION
Avoid decayed wood because chrome azurol-S is an indicator for some types of wood decaying fungi.
PROCEDURE
Add enough thin heartwood shavings to cover the bottom of a clean vial which is approximately 20 x 70 mm. Do not use splinters or chips, because the extraction time is much longer than for shavings. Cover shavings to a depth of approximately 20 mm (approximately 5 ml) with distilled water that is buffered at a pH of 6.86. Packets of buffering agents are available from most scientific supply companies so that only the contents of a packet need to be added to 500 or 1000 ml of distilled water to obtain the desired pH.
Cover the vial and shake vigorously for 10 to 15 seconds. If natural saponins are present in large amounts, tiny bubbles or 'froth' (like foam on a glass of beer) will be formed. Allow the vial to stand for approximately 1 minute from the end of shaking. If 'froth' still completely covers the surface of the solution, the test is positive. If 'froth' or bubbles form and then disappear within 1 minute, the test is negative. If only some froth remains around the edge of the vial (i.e., forming a ring of 'froth', but does not cover the entire surface, the test is weakly positive.
COMMENTS
Positive 'froth' test reactions are produced by, e.g., Mora spp. (Caesalpiniaceae), Enterolobium cyclocarpum, Lysiloma bahamensis, Pseudosamanea spp. (Mimosaceae), Dipholis spp., Mastichodendron spp., and many other species of Sapotaceae.
Weakly positive reactions (ring of froth) are produced by, e.g., Peltophorum spp. (Caesalpiniaceae), Kiggelaria spp. (Flacourtiaceae), Ekebergia spp., Entandrophragma spp. (Meliaceae), Acacia nigrescens (Mimosaceae), Millettia spp. (Papilionaceae), and Berchemia spp. (Rhamnaceae).
For more information, see Dyer (1988), Quirk (1983), Cassens & Miller (1981).
Partial ash = ash that shrinks in size in comparison to the original splinter, has a tendency to drift away, and usually feels gritty when rubbed between the fingers.
Charcoal = the blackened and charred remains of a splinter, which usually burned slowly and/or with difficulty, or the blck and charred remnant of the splinter with a fine thread of black or grey ash which may remain attached.
PROCEDURE
Prepare match-sized (approximately 2 x 2 x 50 mm) splinters from sound outer heartwood, insure the wood is at least air-dry. The splinter must be ignited with a match, and devices (e.g., lighters) producing higher temperatures must be avoided. Ignite the splinter while it is held in a vertical position with a pair of tweezers/forceps. While the splinter is burning, hold it in a horizontal position and turn it slowly.
Some timbers will burn with relative ease (e.g., Populus spp. - Salicaceae), while others may show considerable reluctance (e.g., Eucalyptus paniculata - Myrtaceae). If it appears that the flame will extinguish before the splinter has burned fully, combustion may be aided by gently returning the splinter to a vertical position and then back to horizontal.
After the flame extinguishes, it is important to allow the glowing part of the splinter to extinguish before placing the remnant on a cold surface.
COMMENTS
Certain timbers may crackle or produce bright sparks (e.g., Terminalia catappa - Combretaceae), while others may produce a characteristic smoke coloration (heavy black smoke in Flindersia laevicarpa - Rutaceae) or exude coloured compounds while they burn. All these features may be recorded in a description.
The descriptive classifications for appearance of the burnt splinter are those first recommended by Dadswell & Burnell (1932). Apart from its use in CSIRO keys, Anonymus (1960) has implemented the feature and suggested that it is of little value except in distinguishing between some timbers which are closely related anatomically.
For further information on the burning splinter test, which sofar has only been used on a very limited scale, see Mann (1921), Welch (1922), Swain (1927), Dadswell & Burnell (1932), and Mennega (1948).
In some literature, 'buff' is used to describe splinters that have the colour of pale tanned leather, a yellow brown (state 3), e.g., Eucalyptus paniculata (Myrtaceae).
Cite this publication as: H. G. Richter and M. J. Dallwitz (2000 onwards). 'Commercial timbers: descriptions, illustrations, identification, and information retrieval.' In English, French, German, and Spanish. Version: 4th May 2000. http://biodiversity.uno.edu/delta/.
Dallwitz (1980) and Dallwitz, Paine and Zurcher (1993 onwards, 1995 onwards, 1998) should also be cited (see General references).