The grass genera of the world
Habit, vegetative morphology. Annual, or perennial; caespitose. Culms herbaceous; unbranched above. Culm nodes glabrous. Leaves not basally aggregated; non-auriculate. Leaf blades narrow; not pseudopetiolate; without cross venation; persistent. Ligule a fringed membrane (minutely fringed).
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality.
Inflorescence. Inflorescence of spicate main branches; with capillary branchlets (i.e. capillary rachides); non-digitate. Primary inflorescence branches 12–20. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary, or paired; secund; biseriate; pedicellate.
Female-fertile spikelets. Spikelets about 3 mm long; abaxial; compressed dorsiventrally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present (associated with a characteristic basal prolongation of the solitary glume). Callus long.
Glumes one per spikelet (the upper); shorter than the adjacent lemmas; dorsiventral to the rachis; hairy; with distinct hair tufts and with distinct rows of hairs (with dark brown hairs in 4 rows, between and outside the veins, prolonged into tufts apically); pointed; awnless; non-carinate. Upper glume prolonged downwards into a short spur, this seemingly the extreme of a tendency seen in Digitaria species such as D. flaccida; 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; paleate. Palea of the proximal incomplete florets reduced. The proximal incomplete florets sterile. The proximal lemmas awnless; 5 nerved; more or less equalling the female-fertile lemmas; less firm than the female-fertile lemmas to similar in texture to the female-fertile lemmas (hyaline, densely hairy below and on the margins); not becoming indurated.
Female-fertile florets 1. Lemmas similar in texture to the glumes to decidedly firmer than the glumes; not becoming indurated; entire; pointed; awnless; hairless; non-carinate; having the margins lying flat on the palea; with a clear germination flap; 3 nerved. Palea present; relatively long; entire; awnless, without apical setae; textured like the lemma; not indurated; 2-nerved; 2-keeled. Lodicules present; 2; free; fleshy; glabrous; not or scarcely vascularized. Stamens 3. Anthers not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles basally fused. Stigmas 2; red pigmented.
Fruit, embryo and seedling. Fruit compressed dorsiventrally. Hilum short. Pericarp fused. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells fusiform; having straight or only gently undulating walls (to slightly sinuous in high focus). Microhairs present; panicoid-type; (24–)27–32(–45) microns long; (15–)16–23(–33) microns wide at the septum. Microhair total length/width at septum 5–10.7. Microhair apical cells (4.2–)4.5–4.8(–5.4) microns long. Microhair apical cell/total length ratio 0.55–0.73. Stomata common; 30–36 microns long. Subsidiaries dome-shaped and triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare. Costal short-cells conspicuously in long rows. Costal silica bodies panicoid-type and acutely-angled, or tall-and-narrow (representing incomplete crosses); mostly cross shaped; sometimes sharp-pointed.
Transverse section of leaf blade, physiology. C4; XyMS. Mesophyll with radiate chlorenchyma. Leaf blade adaxially flat. Midrib not readily distinguishable; with one bundle only. Bulliforms not present in discrete, regular adaxial groups (constituting most of the adaxial epidermis). Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures. Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): cf. Panicoideae (as a synonym?); Panicodae; Paniceae; Anthephorinae. 2 species.
Distribution, phytogeography, ecology. Tropical Africa.
References, etc. Leaf anatomical: this project.
Illustrations. • D. readheadii: 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: 13th November 2017. delta-intkey.com/grass’.