The grass genera of the world
Habit, vegetative morphology. Annual, or perennial; rhizomatous, or caespitose. Culms 90–240 cm high; herbaceous; branched above. Culm nodes glabrous. Culm internodes hollow (in B. uniseta). Plants unarmed. Young shoots intravaginal. Leaves not basally aggregated; non-auriculate. Leaf blades linear-lanceolate; broad (to 12 mm wide in B. uniseta), or narrow; flat; pseudopetiolate, or not pseudopetiolate; without cross venation. Ligule a fringe of hairs. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence axillary, compound paniculate (with racemelets each represented by a single spikelet-plus-bristle); espatheate (but sometimes closely subtended by a small leaf); not comprising partial inflorescences and foliar organs. Spikelet-bearing axes very much reduced (reduced to a single spikelet with a long, reduced-branch bristle at its base); (i.e. the much reduced racemelets) disarticulating; falling entire. Spikelets subtended by solitary bristles. The bristles deciduous with the spikelets. Spikelets solitary; secund; pedicellate (but the pedicel being presumably the base of the reduced branch); imbricate.
Female-fertile spikelets. Spikelets 2.5–3.5 mm long (in B. uniseta); abaxial; compressed dorsiventrally; planoconvex; falling with the glumes (spikelet and bristle falling from the pedicel); not disarticulating between the florets; with conventional internode spacings. Rachilla terminated by a female-fertile floret. Hairy callus absent. Callus absent.
Glumes two; very unequal; shorter than the spikelets; shorter than the adjacent lemmas; dorsiventral to the rachis; hairless; glabrous; not pointed; awnless; non-carinate; similar (hyaline, rounded or bilobed). Lower glume shorter than the lowest lemma; 0 nerved. Upper glume 0 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. The proximal incomplete florets 1; epaleate; sterile. The proximal lemmas awnless; 5 nerved; similar in texture to the female-fertile lemmas (membranous); not becoming indurated.
Female-fertile florets 1. Lemmas decidedly firmer than the glumes; smooth; not becoming indurated; entire; pointed; awnless, or mucronate; hairless; glabrous; non-carinate; without a germination flap; 3–5 nerved. Palea present; relatively long; entire (truncate); awnless, without apical setae; thinner than the lemma (hyaline); not indurated; 2-nerved; 2-keeled. Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers about 1.5 mm long in B. uniseta; without an apically prolonged connective. Ovary apically glabrous. Styles fused (near the base). Stigmas 2; red pigmented (purple).
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 absent. Mid-intercostal long-cells having markedly sinuous walls. Microhairs present; panicoid-type; 44–54 microns long. Microhair apical cells 24–36 microns long. Microhair apical cell/total length ratio 0.65. Stomata common. Subsidiaries dome-shaped and triangular. Intercostal short-cells absent or very rare. Costal short-cells conspicuously in long rows. Costal silica bodies panicoid-type; cross shaped to dumb-bell shaped, or nodular.
Transverse section of leaf blade, physiology. C4; XyMS. PCR cell chloroplasts centrifugal/peripheral. Mesophyll with radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs, or nodular in section, or adaxially flat; with the ribs more or less constant in size. Midrib conspicuous; having a conventional arc of bundles; with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups, or not present in discrete, regular adaxial groups; in simple fans (or in groups of fairly evenly sized cells, or in irregular groups). Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders absent. Sclerenchyma all associated with vascular bundles.
Culm anatomy. Culm internode bundles in three or more rings.
Phytochemistry. Leaves without flavonoid sulphates (B. uniseta).
Cytology. Chromosome base number, x = 9. 2n = 18. 2 ploid.
Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae (as a synonym of Pennisetum); Panicodae; Paniceae; Cenchrinae. 6 species.
Distribution, phytogeography, ecology. Tropical and southern Africa.
Helophytic; shade species; glycophytic. Riverine woodland.
Economic aspects. Important native pasture species: B. uniseta.
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Puccinia substriata.
References, etc. Leaf anatomical: Metcalfe 1960; photos of B. uniseta provided by R.P. Ellis.
Illustrations. • B. uniseta var. montana: Jacques-Félix, 1962. • B. laxior: Rose Innes, Ghana Grasses (1977)
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’.