| # The grass genera of the world |

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

### Elytrostachys McClure

Habit, vegetative morphology. Scrambling, sympodial perennial. The flowering culms leafy. Culms woody and persistent; scandent to not scandent (‘culms self-supporting below, typically weak and pendulous or clambering above’); branched above. Buds from which the primary culm branches arise 1. Primary branches 11–20; clumped. The branching dendroid. Culm leaf sheaths present; persistent; where recorded, not conspicuously auriculate. Culm leaves with conspicuous blades. Culm internodes hollow. Rhizomes pachymorph. Plants unarmed. Leaves not basally aggregated; with auricular setae. Leaf blades broad; pseudopetiolate; cross veined, or without cross venation; disarticulating from the sheaths; rolled in bud. Contra-ligule absent.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. Viviparous.

Inflorescence. Inflorescence indeterminate; with pseudospikelets; of pseudospikelet clusters terminating leafy or leafless axes; spatheate; a complex of ‘partial inflorescences’ and intervening foliar organs. Spikelet-bearing axes paniculate to capitate; persistent. Spikelets not secund.

Female-fertile spikelets. Spikelets unconventional; lanceolate; compressed laterally (?); disarticulating above the glumes; with a distinctly elongated rachilla internode above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus absent.

Glumes two (in accordance with the definition of glumes applied here); very unequal; shorter than the adjacent lemmas; awnless; 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, or 2. Lemmas not becoming indurated; entire; pointed, or blunt; awnless, or mucronate (?). Palea present; relatively long; awnless, without apical setae; not indurated; 2-keeled (sulcate). Palea keels wingless. Lodicules present; 3; free; membranous; ciliate; not toothed; heavily vascularized. Stamens 6. Ovary apically glabrous; with a conspicuous apical appendage. The appendage broadly conical, fleshy. Styles fused (the ovary attenuate to the stigmas). Stigmas 2.

Fruit, embryo and seedling. Fruit longitudinally grooved. Hilum long-linear. Pericarp thick and hard (leathery, thickened at the apex); fused.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous (and the intercostal zones with broad stomatal and astomatal bands). Papillae present; costal and intercostal. Intercostal papillae over-arching the stomata (almost covering them); several per cell (mostly with a single median row of 6–10 circular or somewhat bifurcated papillae per long-cell). Long-cells markedly different in shape costally and intercostally (the costals narrower); of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type; 57–60 microns long; 6–6.3 microns wide at the septum. Microhair total length/width at septum 9.5–10. Microhair apical cells 36–40.5 microns long. Microhair apical cell/total length ratio 0.6–0.7. Stomata common; 21–24 microns long. Subsidiaries triangular. Intercostal short-cells common (in the astomatal regions); not paired (solitary); not silicified. Macrohairs present costally, a few prickles present costally and intercostally. Crown cells absent. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies scarce, tall-and-narrow to crescentic.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with arm cells; with fusoids. The fusoids external to the PBS. Leaf blade adaxially flat. Midrib conspicuous; having complex vascularization (one large bundle, and assorted small ones). The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups (with a large group in the middle of each intercostal zone); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’ (all the bundles with a conspicuous ‘anchor’). Sclerenchyma not all bundle-associated (there being adaxial hypodermal fibres lining the sides of the bulliforms, but no abaxial groups opposite them). The ‘extra’ sclerenchyma in adaxial groups; adaxial-hypodermal, contiguous with the bulliforms.

Classification. Watson & Dallwitz (1994): Bambusoideae; Bambusodae; Bambuseae. Soreng et al. (2015): Bambusoideae; Bambusodae; Bambuseae; Arthrostylidiinae. 2 species.

Distribution, phytogeography, ecology. South America: Honduras to Venezuela.

Mesophytic; glycophytic. Rain forest.

References, etc. Leaf anatomical: studied by us - E. clavigera McClure.

Illustrations. • Elytrostachys clavigera: McClure, New World Bamboos (1973).

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, and classifications. See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., Macfarlane, T.D., and Dallwitz, M.J. 1992 onwards. The 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. Version: 15th June 2025. delta-intkey.com’.

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