Neurachne R.Br.
From the Greek neuron (nerve) and achne (scale), alluding to the many-nerved glumes.
Habit, vegetative morphology. Perennial; caespitose (from short rhizomes). Culms 15–50 cm high; herbaceous. Culm nodes hairy, or glabrous. Culm internodes solid. Young shoots extravaginal and intravaginal (the primary shoots extravaginal, each terminating in a tuft of intravaginal culm shoots). Leaves mostly basal; non-auriculate. Leaf blades linear (to very narrowly so); narrow; 0.9–3.5 mm wide; flat, or rolled; exhibiting multicellular glands abaxially. The abaxial leaf blade glands intercostal. Leaf blades without cross venation; persistent; rolled in bud; a fringe of hairs.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite and sterile (the lowermost being reduced).
Inflorescence. Inflorescence a single spike (almost, in N. munroi), or a single raceme (spike-like, or even capitate to ovoid in N. alopecuroidea and N. minor); contracted; capitate, or more or less ovoid, or spicate; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; not secund; not two-ranked (spiralled); sessile (or almost so), or subsessile, or pedicellate (the pedicels short). Pedicel apices oblique, or discoid, or cupuliform.
Female-sterile spikelets. Several of the lowermost spikelets generally much reduced, closer together and more persistent.
Female-fertile spikelets. Spikelets 5–13 mm long (erect); lanceolate; abaxial; compressed dorsiventrally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present. The callus hairs white (very conspicuous, long).
Glumes two; more or less equal; long relative to the adjacent lemmas (exceeding them); dorsiventral to the rachis; hairy (especially marginally); pointed (acuminate); awned, or awnless; very dissimilar to similar (both rigidly membranous, ovate-acuminate to lanceolate-subulate and becoming hardened towards the base, the lower ciliate or not, the upper with a dense narrow sub-marginal beard of long white hairs on each side below). Lower glume 3–7 nerved. Upper glume 7–13 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate. Palea of the proximal incomplete florets fully developed (except occasionally in N. alopecuroidea). The proximal incomplete florets male. The proximal lemmas awnless; 5–7 nerved; more or less equalling the female-fertile lemmas; similar in texture to the female-fertile lemmas to decidedly firmer than the female-fertile lemmas; not becoming indurated.
Female-fertile florets 1. Lemmas less firm than the glumes (membranous to hyaline, in N. munroi smaller and flimsier than the palea); smooth; not becoming indurated (hyaline or membranous); white in fruit; awnless; hairless; non-carinate; having the margins lying flat on the palea; without a germination flap; 0–5 nerved. Palea present; relatively long; entire; awnless, without apical setae; textured like the lemma; not indurated; 2-nerved. Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers not penicillate. Ovary glabrous. Styles fused. Stigmas 2 (but three styles, one usually reduced but forming an appendage on the grain); white, or red pigmented.
Fruit, embryo and seedling. Fruit small; trigonous. Hilum short. Embryo large. Endosperm containing only simple starch grains. Embryo without an epiblast; with a scutellar tail; with a negligible mesocotyl internode.
First seedling leaf with a well-developed lamina. The lamina broad; supine.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular (or at least, not fusiform); having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type. Microhair apical cell wall thinner than that of the basal cell and often collapsed. Microhairs (39–)45–68(–69) microns long. Microhair basal cells 21 microns long. Microhairs (6–)7.2–12(–15) microns wide at the septum. Microhair total length/width at septum 4.6–9.1, or 11 (N. tenuifolia). Microhair apical cells (15–)22–33(–34.5) microns long. Microhair apical cell/total length ratio 0.36–0.61. Stomata common; 27–42 microns long, or 21–27 microns long (N. tenuifolia). Subsidiaries dome-shaped and triangular. Guard-cells overlapping to flush with the interstomatals (a few slightly overlapped in N. alopecuroidea). Intercostal short-cells common; in cork/silica-cell pairs; silicified, or not silicified. Intercostal silica bodies absent. Often with cushion-based macrohairs and/or prickles. Crown cells present (or having structures strongly reminiscent of them), or absent. Costal short-cells conspicuously in long rows (N. alopecuroidea, N. lanigera), or predominantly paired (N. munroi, N. tenuifolia). Costal silica bodies present in alternate cell files of the costal zones; ‘panicoid-type’ (usually), or rounded (the common form in N. tenuifolia, scarce in the other species); not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4 (N. munroi, which has an ‘extra’ sheath, cf. Alloteropsis), or C3 (N. alopecuroidea, N. lanigera, N. queenslandica, N. tenuifolia; N. minor is a C3/C4 intermediate). The anatomical organization when C4 unconventional. Organization of PCR tissue when C4 Alloteropsis type. Biochemical type when C4, NADP–ME (N. munroi); XyMS+ (N. alopecuroidea, N. tenuifolia, N. lanigera, N. queenslandica), or XyMS– (N. munroi). PCR sheath outlines in N. munroi uneven to even. PCR sheath extensions present. Maximum number of extension cells 4. PCR cells with a suberised lamella. PCR cell chloroplasts with well developed grana; centrifugal/peripheral. PBS cells of the C3 species with a suberised lamella (lanigera?), or without a suberised lamella. Mesophyll with radiate chlorenchyma, or with non-radiate chlorenchyma (N. tenuifolia); Isachne-type (e.g. N. lanigera), or not Isachne-type (e.g. N. alopecuroidea). Leaf blade ‘nodular’ in section (the abaxial ribs more prominent); with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (sometimes associated with/comprising hair cushions); in simple fans, or in simple fans and associated with colourless mesophyll cells to form deeply-penetrating fans. Many of the smallest vascular bundles unaccompanied by sclerenchyma (N. tenuifolia), or all the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (N. tenuifolia), or absent; forming ‘figures’ (N. tenuifolia), or nowhere forming ‘figures’. Sclerenchyma all associated with vascular bundles (apart from strong marginal fibre groups). The lamina margins with fibres.
Phytochemistry. Leaf blade chlorophyll a:b ratio of N. munroi 4.06–4.97.
Cytology. Chromosome base number, x = 9. 2n = 18, 36, and 54 (rarely 37, 53). 2, 4, and 6 ploid (and some aneuploids).
Taxonomy. Panicoideae; Panicodae; Neurachneae.
Distribution, ecology, phytogeography. 6 species; Australia. Xerophytic; species of open habitats; glycophytic. Heath, sandstone, light woodland and scrub.
Australian. Central Australian.
Rusts and smuts. Smuts from Ustilaginaceae. Ustilaginaceae — Ustilago.
References, etc. Morphological/taxonomic: Blake 1972b. Leaf anatomical: for leaf anatomy and photosynthetic pathways, see Hattersley et al. 1982, Hattersley and Roksandic 1983.
Illustrations. • General structure. • General aspect. • Habitat. Neurachne queenslandica. 45K east of Tambo, Queensland. • Habitat. Neurachne munroi. North of Cobar, New South Wales. • Habitat. Neurachne minor. North of Wiluna, Western Australia. • Inflorescence. Neurachne minor. • Inflorescence base. Neurachne alopecuroidea. Reduced basal spikelets. • Detail of spikelet. Neurachne queenslandica. Spikelet partly opened in situ, showing the proximal male-only floret (lower left, with smaller stamens) and the hermaphrodite floret. • Leaf blade transverse section. Neurachne munroi. • Leaf blade transverse section. Neurachne alopecuroidea.
Cite this publication as: Watson, L., and Dallwitz, M. J. (1992 onwards). ‘Grass Genera of the World: Descriptions, Illustrations, Identification, and Information Retrieval; including Synonyms, Morphology, Anatomy, Physiology, Phytochemistry, Cytology, Classification, Pathogens, World and Local Distribution, and References.’ http://biodiversity.uno.edu/delta/. Version: 18th August 1999. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993 onwards, 1998), and Watson and Dallwitz (1994), and Watson, Dallwitz, and Johnston (1986) should also be cited (see References).
