The grass genera of the world
Habit, vegetative morphology. Slender annual. Culms 5–50 cm high; herbaceous; unbranched above. Leaves not basally aggregated; non-auriculate. Leaf blades narrow; 2–2.5 mm wide (and 1–8 cm long); flat; without cross venation. Ligule a fringe of hairs.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; exposed-cleistogamous.
Inflorescence. Inflorescence paniculate; delicate, open; with capillary branchlets; non-digitate; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund.
Female-fertile spikelets. Spikelets 2–2.5 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets. Hairy callus present (small). Callus short.
Glumes two; relatively large; more or less equal (the G2 slightly shorter); shorter than the spikelets to about equalling the spikelets; long relative to the adjacent lemmas (exceeding them); hairless; pointed (acute to acuminate); awnless; carinate; similar (linear-lanceolate, hyaline). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped.
Female-fertile florets 2–5. Lemmas similar in texture to the glumes to decidedly firmer than the glumes (thinly membranous, translucent); not becoming indurated; incised; very shortly 2 lobed (the lobes themselves obtuse or minutely bidentate); not deeply cleft; awned. Awns 1; median; from a sinus; non-geniculate; gently recurving, or flexuous; hairless (scabrid); much longer than the body of the lemma (to about 7 mm long, very slender). Lemmas hairy; carinate; 3 nerved. Palea present; relatively long; entire to apically notched; awnless, without apical setae; not indurated (thinly membranous); 2-nerved; 2-keeled. Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers 0.1–0.3 mm long; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit small (0.8–1 mm long); linear, or ellipsoid; trigonous. Hilum short. Embryo small (about 1/4 of the fruit length).
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells rectangular and fusiform; having markedly sinuous walls (but the sinuations gentle). Microhairs present; panicoid-type (the apical cells all missing in material seen); 30(–37.5) microns long; 5.4 microns wide at the septum. Microhair total length/width at septum 5.56–6.94. Microhair apical cells 16.5–21 microns long. Microhair apical cell/total length ratio 0.55–0.6. Stomata absent or very rare (though surprisingly so, in this relatively thin-walled epidermis); 21–22.5 microns long. Intercostal short-cells absent or very rare (none seen). Costal short-cells conspicuously in long rows (though some files have relatively long short-cells). Costal silica bodies panicoid-type; more or less exclusively dumb-bell shaped (large).
Transverse section of leaf blade, physiology. Almost certainly C3 (though the material seen poor); XyMS+. Leaf blade adaxially flat. Midrib not readily distinguishable; with one bundle only. Bulliforms not present in discrete, regular adaxial groups. Combined sclerenchyma girders present; forming figures (small anchors in the primaries only, the other bundles depauperate in sclerenchyma). Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Arundinoideae; Danthonieae. Soreng et al. (2015): Chloridoideae; Triraphideae. 1 species (H. bullockii).
Distribution, phytogeography, ecology. East tropical Africa.
Shade species; glycophytic. On slopes.
References, etc. Morphological/taxonomic: Hubbard 1967a. Leaf anatomical: studied by us.
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’.