The grass genera of the world
Habit, vegetative morphology. Annual, or perennial; decumbent. Culms 40–300 cm high; herbaceous; self-supporting. Leaves not basally aggregated. Leaf blades linear to lanceolate; broad; 10–40 mm wide; cordate (amplexicaul, in H. cordatus), or not cordate, not sagittate; not pseudopetiolate. Ligule present; a fringed membrane; very short.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; open; with capillary branchlets; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; not in distinct long-and-short combinations.
Female-fertile spikelets. Spikelets 2–3.5 mm long; compressed dorsiventrally; falling with the glumes; with a distinctly elongated rachilla internode between the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes two; very unequal (G1 about a third the length of G2); (the upper) about equalling the spikelets; (the upper) long relative to the adjacent lemmas; hairless; awnless; non-carinate; very dissimilar (G1 much smaller, ovate, basally clasping the spikelet). Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; sterile. The proximal lemmas shortly awned (terminally); less firm than the female-fertile lemmas to similar in texture to the female-fertile lemmas (membranous); not becoming indurated.
Female-fertile florets 1. Lemmas similar in texture to the glumes to decidedly firmer than the glumes (thinly papery); smooth (? - dull); not becoming indurated; entire; pointed, or blunt; awnless; hairless; non-carinate; having the margins lying flat on the palea (enfolding and concealing it). Palea present; tightly clasped by the lemma; awnless, without apical setae; 2-nerved. Lodicules present; 2; fleshy. Stamens 3. Stigmas 2.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals narrow, rectangular); of similar wall thickness costally and intercostally (very thin walled). Intercostal zones without typical long-cells (the cells more or less irregularly isodiametric). Mid-intercostal long-cells having markedly sinuous walls and having straight or only gently undulating walls (often very coarsely and irregularly sinuate). Microhairs present; elongated; clearly two-celled; panicoid-type (but unusual, with a vase-shaped basal cell which narrows abruptly towards the apical cell). Stomata common. Subsidiaries non-papillate; low dome-shaped to triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare. Large, cushion-based macrohairscommon intercostally. Costal short-cells conspicuously in long rows. Costal silica bodies present and well developed; panicoid-type; dumb-bell shaped and nodular.
Transverse section of leaf blade, physiology. C3. Midrib conspicuous; with one bundle only, or having a conventional arc of bundles (depending on the interpretation of its limits, which might take in a small lateral on eiter side); with colourless mesophyll adaxially. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups; in simple fans. Sclerenchyma all associated with vascular bundles.
Phytochemistry. Leaves without flavonoid sulphates (H. chlorochloë).
Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paniceae. 2 species.
Distribution, phytogeography, ecology. Central Africa.
Mesophytic; shade species. In woodland and riverine forest.
Economic aspects. Important native pasture species: H. chlorochloë.
References, etc. Leaf anatomical: this project.
Special comments. Fruit data wanting.
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’.