Athroostachys Bentham
Habit, vegetative morphology. Perennial; rhizomatous. The flowering culms leafy. Culms woody and persistent; scandent; branched above. Primary branches/mid-culm node 3. Culm internodes hollow. Unicaespitose. Rhizomes pachymorph. Plants unarmed. Leaves not basally aggregated; with auricular setae. Leaf blades lanceolate; broad; pseudopetiolate; without cross venation; disarticulating from the sheaths.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; contracted; capitate; spatheate (bracteate, the lower bracts liguliform caudate and foliar up to 3 cm long, the upper being short awned scales 0.5 mm long); not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets readily interpreted, provided the subtending bracts are not regarded as glumes; 10–15 mm long; compressed laterally; disarticulating above the glumes; not disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus absent.
Glumes two; very unequal; shorter than the adjacent lemmas; pointed; awned; similar. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped. Spikelets without proximal incomplete florets.
Female-fertile florets 1. Lemmas entire; pointed; awnless to awned (?- subulate-acuminate); hairy (above). Palea present; relatively long; awnless, without apical setae; 2-nerved; 2-keeled. Lodicules present (their tips subulate-acuminate); 3; free; ciliate (towards their tips); not toothed; heavily vascularized. Stamens 3. Anthers not penicillate; with the connective apically prolonged (the thecae apiculate). Ovary glabrous; with a conspicuous apical appendage. The appendage broadly conical, fleshy. Styles fused. Stigmas 2.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; costal and intercostal. Intercostal papillae over-arching the stomata (and almost completely covering them); several per cell (most long-cells with a median row of conspicuous, quite large, mainly bifurcated papillae). 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; elongated; clearly two-celled; panicoid-type; 60–69 microns long; 8.4–10.5 microns wide at the septum. Microhair total length/width at septum 5.9–7.7. Microhair apical cells 27–33 microns long. Microhair apical cell/total length ratio 0.4–0.48. Stomata common; 24–28.5 microns long. Guard-cells sunken. Intercostal short-cells fairly common (in 291–295,2 places), or absent or very rare (elsewhere); not paired (solitary); not silicified (in the material seen). Large costal prickles present, mostly without basal rosettes. Crown cells absent. Costal short-cells predominantly paired (superposed, often ostensibly solitary). Costal silica bodies poorly developed (and few).
Transverse section of leaf blade, physiology. C3. Mesophyll without adaxial palisade; with arm cells; with fusoids. The fusoids external to the PBS. Leaf blade with distinct, prominent adaxial ribs, or adaxially flat (the ribs very low, wide and flat-topped to scarcely manifest). Midrib not readily distinguishable; with one bundle only. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups (between each bundle pair); in simple fans (the groups very large, with deeply penetrating median cells). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); forming ‘figures’ (some forming slender I’s or ‘anchors’). Sclerenchyma not all bundle-associated (there being small abaxial groups opposite the bulliforms, and adaxial hypodermal fibres lining their sides). The ‘extra’ sclerenchyma in abaxial groups and in adaxial groups; abaxial-hypodermal, the groups isolated and adaxial-hypodermal, contiguous with the bulliforms.
Taxonomy. Bambusoideae; Bambusodae; Bambuseae.
Distribution, ecology, phytogeography. 1 species; Brazil.
Neotropical. Amazon and Central Brazilian.
References, etc. Leaf anatomical: this project.
Special comments. Fruit data wanting.
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).