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The grass genera of the world

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

Ekmanochloa Hitchcock

Habit, vegetative morphology. Erect perennial (with dimorphic culms); caespitose. The flowering culms leafless (at least, with 2–3 bladeless leaves). Culms 30–100 cm high; herbaceous; unbranched above; tuberous (with small ‘corms’). Plants unarmed. Leaves not basally aggregated; non-auriculate; without auricular setae. Sheaths shorter than the internodes, striate, glabrous or pilose distally. Leaf blades of the vegetative culms greatly reduced (sometimes, in E. subaphylla?), or not all greatly reduced; linear-lanceolate, or lanceolate; narrow; 1–4 mm wide (8–55 cm long); not cordate, not sagittate (slightly asymmetric at the base); flat; shortly pseudopetiolate; cross veined (the transverse veins seen to be abundant only at high magnification); disarticulating from the sheaths; rolled in bud. Ligule present (minute); an unfringed membrane (laciniate); truncate; 0.1–0.2 mm long.

Reproductive organization. Plants monoecious with all the fertile spikelets unisexual; without hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; female-only and male-only. The male and female-fertile spikelets on different branches of the same inflorescence (there being a pair of slender racemes, one male the other female). The spikelets overtly heteromorphic.

Inflorescence. Inflorescence of spicate main branches (a pair of conjugate, appressed, slender, unisexual racemes, the male raceme slightly shorter than the female); digitate. Primary inflorescence branches 2. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes ‘racemes’; with very slender rachides (these filiform, slightly flexuose); persistent. Spikelets solitary; secund; shortly pedicellate; not in distinct ‘long-and-short’ combinations.

Female-sterile spikelets. The male spikelets 2.7–3.3 mm long, smaller than the females, ellipsoid, hyaline, reduced to the subequal lemma and palea and flower, the lemma awnless. Rachilla of male spikelets terminated by a male floret. The male spikelets without glumes; without proximal incomplete florets; 1 floreted. The lemmas awnless. Male florets 1; 2 staminate (E. subaphylla), or 3 staminate (the anthers 0.8 mm long).

Female-fertile spikelets. Spikelets 6–9 mm long (0.9 mm wide); lanceolate; compressed dorsiventrally; disarticulating above the glumes (the floret ‘early deciduous’); with conventional internode spacings, or with a distinctly elongated rachilla internode above the glumes (0.5 mm long in A. subaphylla). Rachilla terminated by a female-fertile floret. Hairy callus absent.

Glumes two; very unequal, or more or less equal; shorter than the spikelets, or about equalling the spikelets; shorter than the adjacent lemmas, or long relative to the adjacent lemmas (E. subaphylla having short glumes); hairy, or hairless; awnless; non-carinate; similar (membranous). Lower glume 5 nerved. Upper glume 3 nerved. Spikelets with female-fertile florets only.

Female-fertile florets 1. Lemmas terete, narrowing gradually into the slender awn; decidedly firmer than the glumes (leathery); becoming indurated; entire; pointed (attenuate into the awn); long awned. Awns 1; median; apical; non-geniculate; straight, or flexuous; hairless; much longer than the body of the lemma. Lemmas hairy, or hairless; non-carinate; having the margins inrolled against the palea; with a clear germination flap (?); 5 nerved, or 7 nerved. Palea present; relatively long; tightly clasped by the lemma; awnless, without apical setae; textured like the lemma; 2-nerved. Lodicules present; 3; membranous (flabellate); not or scarcely vascularized. Stamens 0 (no staminodes mentioned). Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Disseminule a free caryopsis. Fruit free from both lemma and palea; small to medium sized (4.2 mm long in E. aristata); brown; fusiform; longitudinally grooved; glabrous. Hilum long-linear (as long as the caryopsis). Embryo small.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present (abundant); costal and intercostal. Intercostal papillae over-arching the stomata; several per cell (fairly large, more or less circular or branched, thick walled, in one or two rows per long-cell and forming rings overlooking the stomatal crypts). Long-cells of similar wall thickness costally and intercostally (fairly thin walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls (the sinuosity coarse). Microhairs present; elongated; clearly two-celled; panicoid-type (the basal cells much elongated); 45–50 microns long. Microhair apical cells 5–14 microns long. Stomata common (but lacking in the mid-intercostal regions); 17–28 microns long. Subsidiaries obscured by the papillae. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies tall-and-narrow and vertically elongated-nodular (slim). With scattered prickles costally and intercostally. Costal short-cells conspicuously in long rows. Costal silica bodies present and well developed; ‘panicoid-type’ (mostly), or oryzoid (a few); cross shaped to dumb-bell shaped (large, short); sharp-pointed, or not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with adaxial palisade (E. aristata), or without adaxial palisade (E. ekmanochloa); with arm cells (but fairly inconspicuous); most definitely without fusoids (in the material seen, cf. Zuloaga et al. 1993). Leaf blade more or less adaxially flat. Midrib conspicuous, or not readily distinguishable; with one bundle only; without colourless mesophyll adaxially. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups; in simple fans (these wide, large celled). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’ (I’s with the main bundles). Sclerenchyma all associated with vascular bundles.

Classification. Watson & Dallwitz (1994): Bambusoideae; Oryzodae; Olyreae. Soreng et al. (2015): Bambusoideae; Bambusodae; Olyreae; Olyrinae. 2 species.

Distribution, phytogeography, ecology. Cuba.

Probably shade species; glycophytic. On limestone rocks and in pinewoods.

References, etc. Morphological/taxonomic: Zuloaga et al. 1993. Leaf anatomical: this project; Zuloaga et al. 1993.

Illustrations. • E. subaphylla: Hitchcock (1936)


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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: 13th November 2017. delta-intkey.com/grass’.

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