Thyrsostachys Gamble
From the Greek thyrsos (a Bacchic wand), probably via the derived botanical term thyrse, and stachyus (relating to inflorescence), alluding to inflorescence form.
Habit, vegetative morphology. Arborescent perennial; caespitose. The flowering culms leafy. Culms 800–1000 cm high; woody and persistent; to 6 cm in diameter; branched above. Primary branches/mid-culm node several. Culm sheaths persistent. Rhizomes pachymorph. Plants unarmed. Leaves not basally aggregated; auricles very small; with auricular setae (these small), or without auricular setae. Leaf blades broad; about 10–15 mm wide (by 7–18 cm long); pseudopetiolate; disarticulating from the sheaths; rolled in bud; an unfringed membrane.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence indeterminate; with pseudospikelets; paniculate (large, compound, thyrsoid, the branch nodes bearing sessile, spatheate clusters each of few pseudospikelets); spatheate (the spikelet groups in the axils of short sheaths); a complex of ‘partial inflorescences’ and intervening foliar organs. Spikelet-bearing axes paniculate; persistent. Spikelets not secund.
Female-fertile spikelets. Spikelets 10–25 mm long; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets.
Glumes one per spikelet, or two; very unequal; shorter than the spikelets; shorter than the adjacent lemmas; hairy; pointed; awnless; similar. Upper glume about 9 nerved (‘about 4 on either side’). Spikelets with incomplete florets. The incomplete florets both distal and proximal to the female-fertile florets. The distal incomplete florets merely underdeveloped (differing from Bambusa in the more reduced terminal floret). Spikelets with proximal incomplete florets. The proximal incomplete florets 1, or 2; paleate (the palea of the lowest floret deeply bifid). Palea of the proximal incomplete florets fully developed. The proximal incomplete florets male. The proximal lemmas awnless; exceeded by the female-fertile lemmas; similar in texture to the female-fertile lemmas.
Female-fertile florets 1. Lemmas papery; not becoming indurated; entire; pointed; awnless, or mucronate (?); hairy; many nerved. Palea present; relatively long; apically notched (less cleft thn in the proximal floret); several nerved; 2-keeled (less clearly so than in the proximal florets). Lodicules present, or absent; when present, 1–3; free; membranous (narrow); ciliate; not toothed. Stamens 6. Anthers not penicillate; shortly with the connective apically prolonged. Ovary glabrous; with a conspicuous apical appendage. The appendage broadly conical, fleshy. Styles fused (into one, the base not hollow - thick, forming beak in fruit). Stigmas 3.
Fruit, embryo and seedling. Fruit medium sized (5 to 10 mm long); not noticeably compressed (cylindrical); smooth (glabrous). Hilum long-linear. Pericarp thick and hard (or at least, crustaceous); free, or fused (?). Embryo small (prominent). Endosperm containing compound starch grains.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present (papillae small, variously shaped). Intercostal papillae over-arching the stomata. Mid-intercostal long-cells having markedly sinuous walls (thin). Microhairs present; panicoid-type. Stomata common (obscured by papillae). Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies saddle shaped. Costal short-cells conspicuously in long rows. Costal silica bodies saddle shaped; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with arm cells; with fusoids. Leaf blade ‘nodular’ in section. Midrib conspicuous; having complex vascularization. Bulliforms present in discrete, regular adaxial groups; in simple fans and associated with colourless mesophyll cells to form deeply-penetrating fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’ (in the large bundles).
Cytology. Chromosome base number, x = 12. 2n = 72. 6 ploid.
Taxonomy. Bambusoideae; Bambusodae; Bambuseae.
Distribution, ecology, phytogeography. 2 species; Burma, Siam. Rain forest.
Paleotropical. Indomalesian. Indian and Indo-Chinese.
References, etc. Leaf anatomical: Metcalfe 1960.
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).