The grass genera of the world
Habit, vegetative morphology. Annual (with prop roots). The flowering culms leafy. Culms about 20–100 cm high; herbaceous; to 1 cm in diameter; unbranched above; about 7 noded. Culm nodes exposed; glabrous. Culm leaves present. Culm internodes solid. Leaves not basally aggregated; non-auriculate. Leaf blades linear; broad; 6–14 mm wide; without cross venation; persistent. Ligule an unfringed membrane; not truncate; 1.5–4 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; overtly heteromorphic (the pedicellate spikelets awnless); in both homogamous and heterogamous combinations (the raceme with two basal, large homogamous pairs, forming an involucre for the triad above).
Inflorescence. Inflorescence spatheate; a complex of partial inflorescences and intervening foliar organs (the short racemes incompletely exserted from the spathes). Spikelet-bearing axes very much reduced (2–2.5 cm long, of few spikelets, the adjacent joints of the basal homogamous pairs entering into the formation of the raceme base; pedicels of the trio basally adnate laterally to the G1 of the female-fertile (sessile) member); paired (permanently continguous); with substantial rachides; disarticulating; disarticulating at the joints (the terminal, female-fertile spikelet falling with the pedicels, the homogamous pairs tardily separating later). Articles non-linear; without a basal callus-knob; appendaged (the terminal disarticulation auriculiform); disarticulating obliquely. Spikelets paired and in triplets (with a terminal triad); not secund; sessile and pedicellate; consistently in long-and-short combinations (the basal two homogenous pairs sessile, the triad comprising 1 sessile and 2 pedicellate spikelets); in pedicellate/sessile combinations (in the triad). Pedicels of the pedicellate spikelets free of the rachis (but fused to the G1 of the sessile spikelet). The shorter spikelets hermaphrodite (terminal), or male-only (basal). The longer spikelets male-only.
Female-sterile spikelets. Rachilla of male spikelets terminated by a male floret. The male spikelets with glumes; without proximal incomplete florets; 1 floreted. The lemmas awnless. Male florets 1; 3 staminate.
Female-fertile spikelets. Spikelets 15–19 mm long; not noticeably compressed to compressed dorsiventrally; falling with the glumes (and with the pedicels). Rachilla terminated by a female-fertile floret. Hairy callus present (densely bearded). Callus long (with long hairs); pointed.
Glumes two; more or less equal; exceeding the spikelets; long relative to the adjacent lemmas; hairy (G1 densely villous at the base); not pointed; awnless; non-carinate; very dissimilar. Lower glume much exceeding the lowest lemma; not two-keeled (below, but shortly two-keeled towards the short broad beak); convex on the back; not pitted; relatively smooth; 11 nerved, or 13 nerved. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; epaleate; sterile. The proximal lemmas awnless; 2 nerved; hyaline; not becoming indurated.
Female-fertile florets 1. Lemmas linear, rolled so that the margins meet, but not enclosing other organs, extending into the awn above; less firm than the glumes (but reduced almost to the awn); not becoming indurated; incised; 2 lobed; not deeply cleft (minutely toothed, the teeth hyaline); awned. Awns 1; median; from a sinus (from between the tiny teeth); twice geniculate; hairy (silky-pubescent); much longer than the body of the lemma; deciduous (or at least falling with the deciduous L2). Awn bases flattened. Lemmas hairy; non-carinate; without a germination flap; 1 nerved. Palea present; conspicuous but relatively short; awnless, without apical setae; thinner than the lemma; not indurated (hyaline); nerveless; 2-keeled. Palea back glabrous. Palea keels wingless; glabrous. Lodicules present; 2; free; fleshy; ciliate, or glabrous; not or scarcely vascularized. Stamens 3. Anthers about 5 mm long; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Stigmas 2.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; intercostal (large, on the interstomatals, conspicuous only in places). Intercostal papillae when present, consisting of one oblique swelling per cell. Long-cells markedly different in shape costally and intercostally (the costals much narrower, more regularly rectangular); of similar wall thickness costally and intercostally (fairly thin walled). Mid-intercostal long-cells fairly regularly rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type. Stomata common. Subsidiaries non-papillate; low dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common (often paired with prickle bases); sometimes in cork/silica-cell pairs; sometimes silicified. Intercostal silica bodies crescentic, cross-shaped, and oryzoid-type. Numerous small, bulbous prickles and occasional cushion-based macrohairs, in the intercostal zones. Costal short-cells conspicuously in long rows. Costal silica bodies present and well developed; panicoid-type; butterfly shaped and dumb-bell shaped.
Transverse section of leaf blade, physiology. C4; XyMS+ to XyMS (XyMS variable). PCR sheath outlines uneven. PCR sheath extensions absent. Leaf blade adaxially flat. Midrib conspicuous; having a conventional arc of bundles (three primaries, with numerous small bundles between); with colourless mesophyll adaxially (and a narrow median adaxial-hypodermal layer of sclerenchyma). The lamina symmetrical on either side of the midrib. Bulliforms not present in discrete, regular adaxial groups (the adaxial epidermis largely bulliform). Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present (with the primaries and larger minor bundles). Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae (?). 1 species (D. seretii).
Distribution, phytogeography, ecology. Tropical Africa.
References, etc. Leaf anatomical: studied by us.
Special comments. Fruit data wanting. Illustrations. • D. dybowskii (as D. seretii): Jacques-Félix, 1962
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’.