The grass genera of the world
Habit, vegetative morphology. Coarse annual, or perennial; caespitose. Culms 50–250 cm high; herbaceous; branched above. Leaves not basally aggregated; non-auriculate; without auricular setae. Leaf blades linear; narrow; 2–9 mm wide ((3-)10–60 cm long); not setaceous (rolled or with revolute margins); without cross venation. Ligule an unfringed membrane; truncate; (0.5–)1–3 mm long. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite and male-only, or hermaphrodite and sterile; overtly heteromorphic (only the female-fertile spikelets awned); in both homogamous and heterogamous combinations (each raceme with 1–6 or more male-only or sterile pairs at the base, then one or more heterogamous pairs above and a heterogamous terminal triad). Plants seemingly inbreeding (the long-pedunculate racemes enclosed in the spatheoles), or outbreeding (?).
Inflorescence. Inflorescence paniculate (of long-exserted racemes gathered into a false panicle); spatheate (and spatheolate); a complex of partial inflorescences and intervening foliar organs (the spathes and spatheoles narrow, with subulate or setaceous tips). Spikelet-bearing axes elongated racemes; the spikelet-bearing axes with 45 spikelet-bearing articles to with more than 10 spikelet-bearing articles ((4-)-18 pairs); paired (in each spatheole); with substantial rachides; disarticulating; disarticulating at the joints. Articles linear; without a basal callus-knob; not appendaged; disarticulating obliquely; somewhat hairy to glabrous. Spikelets paired and in triplets (pairs below, with a terminal heterogamous triad); sessile and pedicellate; consistently in long-and-short combinations (in the upper part of the raceme, those of the lower homogamous pairs all being sessile); in pedicellate/sessile combinations. Pedicels of the pedicellate spikelets free of the rachis. The shorter spikelets hermaphrodite (i.e., in the heterogamous combinations). The longer spikelets male-only, or sterile (rarely).
Female-sterile spikelets. The pedicellate spikelets male or rarely sterile, awnless, with an elongated linear callus. The male spikelets with glumes; 2 floreted. The lemmas awnless.
Female-fertile spikelets. Spikelets 7–11(–12) mm long; not noticeably compressed to compressed dorsiventrally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present. The callus hairs white (short). Callus pointed to blunt.
Glumes two; more or less equal; long relative to the adjacent lemmas; hairy (with white or yellowish hairs); without conspicuous tufts or rows of hairs; awned (the G2, except sometimes in E. androphila); non-carinate; very dissimilar (leathery, the G1 obtuse or truncate, the thinner G2 pointed with an awn or subule, dorsally rounded and grooved). Lower glume not two-keeled; convex on the back; not pitted; relatively smooth; 7 nerved. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. The proximal incomplete florets 1; epaleate; sterile. The proximal lemmas awnless; 2 nerved; more or less equalling the female-fertile lemmas; similar in texture to the female-fertile lemmas (hyaline); not becoming indurated.
Female-fertile florets 1. Lemmas stipitate, with hyaline wings and teeth; less firm than the glumes; not becoming indurated; incised; 2 lobed; deeply cleft; awned. Awns 1; median; from a sinus; geniculate; hairy; much longer than the body of the lemma. Lemmas with the hyaline part ciliate; non-carinate; without a germination flap; 1 nerved. Palea absent. Lodicules present; 2; free (small); fleshy; glabrous. Stamens 3. Anthers not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles basally fused. Stigmas 2.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells mostly markedly different in shape costally and intercostally (the costals generally narrower and more regularly rectangular); of similar wall thickness costally and intercostally. Intercostal zones with typical long-cells to exhibiting many atypical long-cells. Mid-intercostal long-cells rectangular, or rectangular to fusiform; having markedly sinuous walls to having straight or only gently undulating walls. Microhairs present; elongated; clearly two-celled; panicoid-type; of E. grallata, 48–54(–60) microns long; 6 microns wide at the septum. Microhair total length/width at septum 8–10. Microhair apical cells 15–18 microns long. Microhair apical cell/total length ratio 0.3–0.4. Stomata common; of E. grallata 34.5–43.5 microns long. Subsidiaries tall triangular, or dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common (in E. archaelymandra), or absent or very rare (but E. grallata with numerous small prickles); of E. archaelymandra in cork/silica-cell pairs; silicified. Intercostal silica bodies crescentic, or tall-and-narrow. Costal short-cells conspicuously in long rows. Costal silica bodies present and well developed; panicoid-type; mostly dumb-bell shaped.
Transverse section of leaf blade, physiology. C4; XyMS. PCR sheath extensions absent. Mesophyll with radiate chlorenchyma; traversed by columns of colourless mesophyll cells (associated with the arches), or not traversed by colourless columns. Leaf blade with distinct, prominent adaxial ribs, or adaxially flat. Midrib very conspicuous (and abaxially prominent); having a conventional arc of bundles (with several small laterals each side of a usually very large median); with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups to not present in discrete, regular adaxial groups (the epidermis often largely, more or less irregularly bulliform between the costae); sometimes, irregularly in simple fans, or associated with colourless mesophyll cells to form deeply-penetrating fans; associating with colourless mesophyll cells to form arches over small vascular bundles (these especially spectacular in E. androphila). Many of the smallest vascular bundles unaccompanied by sclerenchyma, or all the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (primaries); forming figures (these usually slender, massive in E. androphila). Sclerenchyma all associated with vascular bundles.
Cytology. 2n = 20.
Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae; Anthistiriinae. 4 species.
Distribution, phytogeography, ecology. Tropical Africa.
Mesophytic; shade species, or species of open habitats; glycophytic. Savanna woodland.
Rusts and smuts. Smuts from Tilletiaceae and from Ustilaginaceae. Tilletiaceae Tilletia. Ustilaginaceae Sphacelotheca.
References, etc. Leaf anatomical: studied by us (mostly poor material)- E. androphila (Stapf) Stapf, E. archaelymandra (Jac.-Fél.) W.D. Clayton, E. grallata (Stapf) Clayton, E. subulata Jac.-Fél.
Illustrations. • E. subulata: Jacques-Félix, 1962. • E. androphila: Rose Innes, Ghana Grasses (1977). • E. grallata: Gibbs Russell et al., 1990
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: 11th December 2017. delta-intkey.com/grass’.