The grass genera of the world
Habit, vegetative morphology. Slender annual. Culms 4–16 cm high; herbaceous. Leaves non-auriculate. Leaf blades narrow; flat, or rolled; without cross venation; persistent. Ligule an unfringed membrane; not truncate; 1–3 mm long.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets; exposed-cleistogamous, or chasmogamous.
Inflorescence. Inflorescence paniculate; open; with capillary branchlets; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund.
Female-fertile spikelets. Spikelets 2–3 mm long; compressed laterally to not noticeably compressed; disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension naked (minute). Hairy callus present. Callus short; blunt.
Glumes present; two; more or less equal; exceeding the spikelets; long relative to the adjacent lemmas (exceeding them); pointed (acuminate); awnless; carinate; similar (membranous). Lower glume 3 nerved, or 5 nerved. Upper glume 3 nerved, or 5 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1. Lemmas decidedly firmer than the glumes (thinly leathery); becoming indurated (at least by contrast with Agrostis); incised; 2 lobed (shortly bidentate); not deeply cleft; awned. Awns 1; median; dorsal; from near the top, or from well down the back; geniculate; much longer than the body of the lemma; entered by one vein. Lemmas hairless; glabrous, or scabrous; non-carinate; having the margins inrolled against the palea; without a germination flap; 5–7 nerved. Palea present; relatively long; tightly clasped by the lemma; minutely apically notched; awnless, without apical setae; not indurated (hyaline/membranous); 2-nerved; 2-keeled. Lodicules present; 2; free; membranous; glabrous; toothed, or not toothed; not or scarcely vascularized. Stamens 3. Ovary glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit small (1.2 mm long); not grooved; compressed dorsiventrally, or not noticeably compressed. Hilum short. Embryo small. Endosperm hard; with lipid; containing compound starch grains.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (costals shorter, bulbous); of similar wall thickness costally and intercostally (thin-walled). Mid-intercostal long-cells fusiform; having straight or only gently undulating walls. Microhairs absent. Stomata common; 42–57 microns long. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells absent or very rare. Costal short-cells neither distinctly grouped into long rows nor predominantly paired (mostly solitary or paired). Costal silica bodies horizontally-elongated crenate/sinuous (many deeply crenate, some almost nodular, sometimes with pointed corners); sharp-pointed (many of the crenate/nodular silica-bodies have pointed corners).
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with radiate chlorenchyma (in places); without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs to nodular in section; with the ribs more or less constant in size (low, round-topped). Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (in the furrows); in simple fans (these broad). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent (mostly strands only). Sclerenchyma all associated with vascular bundles.
Taxonomy. Pooideae; Poodae; Aveneae.
Distribution, ecology, phytogeography. 2 species; on mountains of Tropical West Africa. Mesophytic; species of open habitats; glycophytic. Mountain grassland.
Paleotropical. African. West African Rainforest.
References, etc. Leaf anatomical: this project.
Illustrations. • Abaxial epidermis of leaf blade (H. cameroonensis). • Leaf blade transverse section (H. cameroonensis)
This description is offered for casual browsing only. We strongly advise against extracting comparative information from it. This is much more easily achieved using 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 specified attributes, summaries of attributes within groups of taxa, geographical distribution, classification, and species sampled for anatomy.
Cite this publication as: ‘Watson, L., 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: 18th December 2012. http://delta-intkey.com’.