The grass genera of the world
Including Beckera Fresen.
Habit, vegetative morphology. Annual, or perennial; stoloniferous, or decumbent. Culms 15–180 cm high; herbaceous. Culm nodes glabrous. Leaves not basally aggregated; non-auriculate. Leaf blades narrow; without cross venation; persistent. Ligule membranous; 1 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality.
Inflorescence. Inflorescence of spicate main branches (slender spiciform racemes), or a single raceme; digitate, or non-digitate (when of a single raceme); espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; secund; pedicellate.
Female-fertile spikelets. Spikelets 2–4 mm long; adaxial; compressed dorsiventrally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes present; two; minute; more or less equal; shorter than the adjacent lemmas; dorsiventral to the rachis; not pointed; awnless; similar (reduced to small, rotund scales). Lower glume 0 nerved. Upper glume 0 nerved. 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 usually awned; decidedly exceeding the female-fertile lemmas (equalling the spikelet).
Female-fertile florets 1. Lemmas not becoming indurated (membranous); entire; pointed; awnless, or mucronate, or awned. Awns when present, 1; apical; non-geniculate; much shorter than the body of the lemma. Lemmas hairless; non-carinate; having the margins lying flat on the palea; 3–5 nerved. Palea present; conspicuous but relatively short (less than half the floret length). Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers not penicillate. Ovary apically glabrous. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small; compressed dorsiventrally. Hilum short. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present. Mid-intercostal long-cells having markedly sinuous walls. Microhairs present; panicoid-type; 28–45 microns long. Microhair apical cells 16–27 microns long. Microhair apical cell/total length ratio 0.55. Stomata common. Subsidiaries high dome-shaped and triangular. Intercostal short-cells absent or very rare. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies infrequent, panicoid-type; nodular; not sharp-pointed.
Transverse section of leaf blade, physiology. C4; XyMS. Mesophyll with radiate chlorenchyma. Leaf blade adaxially flat. Midrib conspicuous; having a conventional arc of bundles; with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups (the epidermis partly, irregularly bulliform). Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present. Sclerenchyma all associated with vascular bundles.
Culm anatomy. Culm internode bundles scattered.
Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae (Arthropogoneae). Soreng et al. (2015): Panicoideae; Panicodae; Paniceae; Cenchrinae. 4 species.
Distribution, phytogeography, ecology. Tropical East Africa.
Economic aspects. Important native pasture species: S. polystachya.
Rusts and smuts. Rusts Puccinia.
References, etc. Leaf anatomical: Metcalfe 1960, and 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’.