The grass genera of the world
Habit, vegetative morphology. Annual; decumbent. Culms herbaceous; branched above. Culm nodes glabrous. Leaves not basally aggregated; non-auriculate. Leaf blades linear to lanceolate (broadly linear to narrowly lanceolate); broad to narrow; 4–15 mm wide (to 14 cm long); without cross venation; persistent. Ligule an unfringed membrane (firm); truncate; 1 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence of spicate main branches. Primary inflorescence branches 2–4. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; secund; pedicellate.
Female-fertile spikelets. Spikelets 5 mm long; compressed dorsiventrally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes two; very unequal; shorter than the adjacent lemmas; hairy; (the upper) awned (attenuate into very long, filiform, flexuous awns); non-carinate; very dissimilar. Lower glume 0–1 nerved. Upper glume 2–4 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; epaleate; sterile. The proximal lemmas awned (identically with G2); 6 nerved; more or less equalling the female-fertile lemmas; similar in texture to the female-fertile lemmas; not becoming indurated.
Female-fertile florets 1. Lemmas less firm than the glumes to similar in texture to the glumes; not becoming indurated; entire; pointed; mucronate (with a terminal subule); hairless; non-carinate; having the margins lying flat on the palea; with a clear germination flap; 5 nerved. Palea present; relatively long; entire; 2-nerved; 2-keeled. Lodicules present; 2; free; fleshy; glabrous; not or scarcely vascularized. Stamens 3; with free filaments. Anthers not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles fused. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small; compressed dorsiventrally. Hilum short. Embryo large; not waisted.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present. Intercostal papillae not over-arching the stomata; consisting of one oblique swelling per cell. Intercostal zones exhibiting many atypical long-cells. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type. Stomata common (but confined to single files bordering veins). Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare. Costal short-cells conspicuously in long rows. Costal silica bodies panicoid-type.
Transverse section of leaf blade, physiology. C3; XyMS+. Leaf blade nodular in section; with the ribs more or less constant in size. Midrib conspicuous; having a conventional arc of bundles. Bulliforms not present in discrete, regular adaxial groups (these present only in irregular groups); in irregular groups. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures. Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paniceae; Cenchrinae. 1 species (A. volkensii).
Distribution, phytogeography, ecology. Tropical Africa.
Mesophytic; shade species; glycophytic. Montane forest.
References, etc. Leaf anatomical: studied by us.
Illustrations. • A. volkensii: Jacques-Félix, 1962
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’.