The grass genera of the world

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

Drake-Brockmania Stapf

~ Dinebra sensu lato

Excluding Heterocarpha

Habit, vegetative morphology. Annual, or perennial; caespitose, or decumbent. Culms 5–65 cm high; herbaceous; branched above, or unbranched above. Plants unarmed. Young shoots intravaginal. Leaves not basally aggregated; non-auriculate. Leaf blades linear; narrow; flat; exhibiting multicellular glands abaxially (at the base of hairs). The abaxial leaf blade glands intercostal. Leaf blades without cross venation. Ligule an unfringed membrane; truncate; 0.7–1.5 mm long.

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

Inflorescence. Inflorescence of spicate main branches (of short, broad spikes on a central axis); contracted; non-digitate (the axis short), or subdigitate. Primary inflorescence branches 3–6. Inflorescence with axes ending in spikelets. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes disarticulating; falling entire (the spikes deciduous). Spikelets secund; biseriate; subsessile; imbricate.

Female-fertile spikelets. Spikelets 6–14 mm long; strongly compressed laterally; disarticulating above the glumes (but the spikes falling first); eventually disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus absent.

Glumes two; very unequal (G2 conspicuous, spreading); shorter than the spikelets; (the upper) long relative to the adjacent lemmas (almost as long); awnless; carinate; glumes lanceolate. Lower glume much exceeding the lowest lemma; 1–5 nerved. Upper glume 7–17 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped.

Female-fertile florets 5–18. Lemmas lemma papery; not becoming indurated; entire; pointed; mucronate (or cuspidate); hairy (villous below on keel and margins); carinate; without a germination flap; (3–)5–7 nerved. Palea present; relatively long; entire to apically notched; awnless, without apical setae; 2-nerved; 2-keeled. Palea keels winged, or wingless. Lodicules present; 2; glabrous. Stamens 3. Anthers not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit ellipsoid; trigonous. Hilum short. Pericarp loosely adherent (removable when wet). Embryo large.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; costal and intercostal. Intercostal papillae over-arching the stomata (slightly), or not over-arching the stomata; consisting of one oblique swelling per cell to consisting of one symmetrical projection per cell (thick-walled). Long-cells markedly different in shape costally and intercostally (the costals longer and narrower). Intercostal zones with typical long-cells to exhibiting many atypical long-cells (many of them quite short). Mid-intercostal long-cells rectangular; having markedly sinuous walls to having straight or only gently undulating walls. Microhairs present; more or less spherical; ostensibly one-celled; chloridoid-type (obviously glandular). Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs 21–22.5(–26) microns long. Microhair basal cells 9 microns long. Microhair total length/width at septum 1. Microhair apical cell/total length ratio 0.5. Stomata common; 15–18 microns long. Subsidiaries dome-shaped (mostly), or triangular (a few). Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare (but lots of short ‘long-cells’); not paired. Intercostal silica bodies absent. With a few costal prickles. Crown cells absent. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; ‘panicoid-type’; mostly dumb-bell shaped.

Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.

C4; XyMS+. PCR sheaths of the primary vascular bundles interrupted; interrupted both abaxially and adaxially. PCR sheath extensions absent. Leaf blade ‘nodular’ in section (with large and small ‘nodules’). Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (these infrequent); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with most bundles); forming ‘figures’ (with most bundles). Sclerenchyma all associated with vascular bundles.

Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae. 1 species (D. somalensis).

Distribution, phytogeography, ecology. Eastern Africa.

Mesophytic; species of open habitats. Damp places in savanna.

References, etc. Morphological/taxonomic: Phillips 1974. Leaf anatomical: studied by us.

Special comments. Generic circumscriptions around Brachychloa, Drake-Brockmania and Heterocarpha seem problematical, especially in the absence of anatomical data for H. haareri and B. fragilis. Illustrations. • D. somalensis: Ibrahim & Kabuye, Kenya Grasses (1987)

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.’.