Thysanolaena Nees
From the Greek thysanos (fringe) and chlaina (cloak), referring to a fringed upper lemma.
Including Myriachaeta Moritzi
Habit, vegetative morphology. Tufted perennial; reedlike. Culms 150–400 cm high; woody and persistent; branched above (shrubby). Culm internodes solid. Leaves not basally aggregated; auriculate, or non-auriculate. Leaf blades lanceolate (-acuminate); somewhat leathery; broad; (30–)40–70(–100) mm wide (up to 60 cm long); somewhat cordate (amplexicaul); flat; pseudopetiolate; cross veined; disarticulating from the sheaths; rolled in bud; an unfringed membrane, or a fringed membrane (minutely ciliolate); truncate (cartilaginous). Contra-ligule present.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate (large, with numerous tiny spikelets); open (contracted on the primary branches); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes disarticulating (pedicels and ultimate branchlets disarticulating). Spikelets secund; pedicellate.
Female-fertile spikelets. Spikelets 1.2–1.8 mm long; compressed laterally (and somewhat asymmetric); disarticulating above the glumes and falling with the glumes (falling with the pedicels, but also disarticulating above the glumes); tardily disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret (ending in a flattened process 0.5 mm long, with a flattened tip). Hairy callus absent.
Glumes two; relatively large; very unequal to more or less equal; shorter than the spikelets; shorter than the adjacent lemmas; not pointed (obtuse); awnless; non-carinate; similar (broadly oval, hyaline). Lower glume 0–1 nerved. Upper glume 0–1 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets, or both distal and proximal to the female-fertile florets (proximal incomplete floret always present, distal rudiment present or absent). The distal incomplete florets when present, merely underdeveloped. The proximal incomplete florets 1; epaleate; sterile. The proximal lemmas acuminate, glabrous; awnless (acuminate); 1–3 nerved; decidedly exceeding the female-fertile lemmas (equalling the spikelet); less firm than the female-fertile lemmas (membranous); not becoming indurated.
Female-fertile florets 1. Lemmas decidedly firmer than the glumes; becoming indurated (firmer than the L1); entire; pointed; awnless, or mucronate; hairy; non-carinate; without a germination flap; 3 nerved. Palea present; conspicuous but relatively short; apically notched; awnless, without apical setae; not indurated (thin); 2-nerved; 2-keeled. Lodicules present; 2; free; fleshy; glabrous; not or scarcely vascularized. Stamens 2–3. Anthers 0.8 mm long; not penicillate. Ovary glabrous. Styles free to their bases. Stigmas 2; red pigmented.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small; ellipsoid, or subglobose; not noticeably compressed. Hilum short. Embryo large; not waisted.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present (but very scarce in material seen: perhaps variable in frequency, cf. Phragmites?); panicoid-type. Stomata common. Subsidiaries low dome-shaped, or triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies tall-and-narrow, or crescentic, or vertically elongated-nodular, or oryzoid-type. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; cross shaped, butterfly shaped, and dumb-bell shaped; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade; with arm cells. Leaf blade ‘nodular’ in section; with the ribs more or less constant in size. Midrib conspicuous; having a conventional arc of bundles. Bulliforms present in discrete, regular adaxial groups (between each bundle pair); consistently in simple fans (in the material seen, the fans large with a deeply penetrating median cell). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’ (most of the bundles with a smallish I or T). Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 11, or 12 (?).
Taxonomy. Centothecoideae, or Arundinoideae; Arundineae (?).
Distribution, ecology, phytogeography. 1 species; tropical Asia. Species of open habitats; glycophytic. On mountains.
Paleotropical. Indomalesian. Indian, Indo-Chinese, Malesian, and Papuan.
Economic importance. Important native pasture species: T. maxima.
References, etc. Leaf anatomical: Metcalfe 1960; this project.
Illustrations. • Abaxial epidermis of leaf blade. Thysanolaena maxima. • Abaxial epidermis of leaf blade. • Transverse section of leaf blade
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).
