The grass genera of the world
Habit, vegetative morphology. Perennial; caespitose. Culms 20–75 cm high; herbaceous; unbranched above. Culm nodes glabrous. Plants unarmed. Young shoots intravaginal. Leaves not basally aggregated; non-auriculate. Leaf blades linear; narrow; 2–5 mm wide; exhibiting multicellular glands abaxially (maybe at base of hairs?). The abaxial leaf blade glands intercostal. Leaf blades without cross venation; persistent. Ligule a fringe of hairs. Contra-ligule present (of inconspicuous hairs, more pronounced laterally).
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence a single raceme, or paniculate, or a false spike, with spikelets on contracted axes (bottlebrush-like, spiciform, the lowermost pedicels sometimes branching, the solitary or paired spikelets interpretable as reduced clusters). Inflorescence with axes ending in spikelets. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent (the main axis persistent), or disarticulating (if the deciduous spikelet-plus-pedicel is interpreted as a reduced branch); (if interpreted as reduced branches) falling entire. Spikelets almost in verticils on the rachis; secund (symmetrically disposed, but turned to one side and deflexing).
Female-fertile spikelets. Spikelets 5–11 mm long; purplish; strongly compressed laterally; falling with the glumes (abscising near the bases of the pedicels, to leave hairy stumps (true pedicels?) on the rachis); disarticulating between the florets; with distinctly elongated rachilla internodes between the florets (curved). Rachilla prolonged beyond the uppermost female-fertile floret; hairless (glabrous, flexuous). Hairy callus present (consisting of the main part of the pedicel). Callus long; pointed.
Glumes present; two; very unequal (G1 about two-thirds the length of G2); shorter than the spikelets; shorter than the adjacent lemmas; hairless; glabrous; not pointed (rounded); awnless; carinate; similar (membranous, narrow, oblong). Lower glume not two-keeled; 1 nerved. Upper glume 1 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets, or both distal and proximal to the female-fertile florets (the L1 being smaller than those above, and sometimes lacking stamens in the material seen). The distal incomplete florets merely underdeveloped. The proximal incomplete florets when present, 1.
Female-fertile florets 4–16 (increasing in size acropetally). Lemmas enlarged at the base, then acuminate to the tip; similar in texture to the glumes to decidedly firmer than the glumes (membranous, or cartilaginous below); smooth; not becoming indurated; entire; pointed; mucronate, or awned. Awns when present, 1; apical; geniculate; much shorter than the body of the lemma. Lemmas hairless; glabrous; carinate; without a germination flap; 3 nerved. Palea present; conspicuous but relatively short (to about two-thirds of the lemma length); entire; awnless, without apical setae; not indurated (membranous); 2-nerved (and deeply hollowed between); 2-keeled. Palea keels winged (the wings ciliolate). Lodicules present; 2; free; fleshy; glabrous. Stamens 3; with free filaments (short). Anthers relatively long; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2; white.
Fruit, embryo and seedling. Fruit small (0.75–1.3 mm long); compressed laterally. Hilum short. Pericarp fused. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally (medium thick walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls (pitted). Microhairs present; elongated; clearly two-celled; panicoid-type to chloridoid-type (the apical cells round-tipped, not collapsing, short (chlorioid) to quite elongated (panicoid)). Microhair apical cell wall thinner than that of the basal cell but not tending to collapse. Microhair basal cells 18–21 microns long. Microhair total length/width at septum 4. Microhair apical cell/total length ratio 0.5. Stomata common. Subsidiaries high dome-shaped and triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; not paired (mostly solitary); not silicified (apparently). Intercostal silica bodies absent. Costal short-cells predominantly paired. Costal silica bodies present throughout the costal zones (mostly), or present in alternate cell files of the costal zones; saddle shaped (plus various imperfect forms), or rounded (merging into broad saddles), or crescentic (a few).
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheaths of the primary vascular bundles interrupted; interrupted abaxially only. PCR sheath extensions present. Maximum number of extension cells 1–2. Leaf blade adaxially flat. Midrib conspicuous (somewhat: a wider abaxial rib and a large anchor of abaxial sclerenchyma); with one bundle only. Bulliforms present in discrete, regular adaxial groups (between all the bundles); in simple fans (but the median cels of the simple fans deeply penetrating). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the main bundles); forming figures (all the main bundles). Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Eragrostideae; Eragrostidinae. 2 species.
Distribution, phytogeography, ecology. Tropical Africa.
Species of open habitats. Savanna.
References, etc. Leaf anatomical: this project.
Illustrations. • H. schimperi: Jacques-Félix, 1962. • H. schimperi, abaxial epidermis of leaf blade: this project. • H. schimperi, abaxial epidermis of leaf blade: this project
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’.