The grass genera of the world
Including Plazerium Kunth
Habit, vegetative morphology. Perennial; caespitose. Culms 40–120 cm high; herbaceous; unbranched above. Culm nodes hairy, or glabrous. Culm internodes hollow. Leaves mostly basal; non-auriculate. Leaf blades linear; narrow; flat (usually), or folded (rarely); without cross venation. Ligule a fringed membrane, or a fringe of hairs.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite and female-only; more or less homomorphic (but the pedicelled members smaller); all in heterogamous combinations.
Inflorescence. Inflorescence of spicate main branches, or paniculate (of spiciform racemes, in a raceme or panicle, with tawny-red hairs); contracted (narrow); non-digitate. Primary inflorescence branches 6–12. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes racemes; solitary; with substantial rachides; disarticulating; disarticulating at the joints. Articles linear to non-linear (clavate); not appendaged; disarticulating transversely; densely long-hairy (at the disarticulation line). Spikelets paired; sessile and pedicellate; consistently in long-and-short combinations; in pedicellate/sessile combinations. Pedicels of the pedicellate spikelets free of the rachis. The shorter spikelets hermaphrodite. The longer spikelets female-only.
Female-fertile spikelets. Spikelets compressed dorsiventrally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present.
Glumes two; more or less equal; long relative to the adjacent lemmas; free; hairy; awnless; non-carinate; very dissimilar (the G2 thinner, not 2-keeled). Lower glume two-keeled; convex on the back; not pitted; relatively smooth; indistictly many nerved. Upper glume 1 nerved, or 3 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; 0 nerved; decidedly exceeding the female-fertile lemmas; similar in texture to the female-fertile lemmas (hyaline); not becoming indurated.
Female-fertile florets 1. Lemmas less firm than the glumes (hyaline); not becoming indurated; entire to incised (truncate to serrate); not deeply cleft; awnless; non-carinate; without a germination flap; 0 nerved. Palea absent. Lodicules present; 2; free; fleshy; glabrous. Stamens 3 (in the sessile spikelets, rudimentary in the pedicellate spikelets). Anthers not penicillate; without an apically prolonged connective. Ovary apically glabrous. Stigmas 2; red pigmented, or brown.
Fruit, embryo and seedling. Hilum short. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally to markedly different in shape costally and intercostally (the costals narrower); of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular and fusiform; having markedly sinuous walls. Microhairs absent. Stomata common; 24–28.5 microns long. Subsidiaries triangular. Guard-cells overlapped by the interstomatals (sic). Intercostal short-cells absent or very rare (unless the rows over minor veins called intercostal). With numerous complex-based macrohairs over the veins. Costal short-cells predominantly paired. Costal silica bodies panicoid-type, or acutely-angled (a few); short dumb-bell shaped, or cross shaped; sharp-pointed (a few crosses of Isachne type).
Transverse section of leaf blade, physiology. C4; XyMS (but the PCR sheath cell walls very thick and pitted, resembling a mestome sheath). PCR cell chloroplasts centrifugal/peripheral. Leaf blade adaxially flat. Midrib conspicuous; having a conventional arc of bundles (one large keel bundle, 3 small ones on each side); with colourless mesophyll adaxially (this colourless tissue lignified). Bulliforms present in discrete, regular adaxial groups (the groups of large cells); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (nearly all bundles); forming figures (mid-rib constituting a large anchor. Other main bundles with Is). Sclerenchyma all associated with vascular bundles.
Cytology. 2n = 20.
Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae. 7 species.
Distribution, phytogeography, ecology. Tropical America and tropical Africa.
Helophytic; species of open habitats; glycophytic. In swamps and moist places.
References, etc. Leaf anatomical: this project.
Illustrations. • E. brachypogon: Jacques-Félix, 1962. • E. holcoides, as Andropogon: Kunth (1829), Rev. des Graminées. • E. pallida, as Saccharum munroanum: Wood, Natal Plants 2 (1904). • General aspect (E. pallida): Gibbs Russell et al., 1990. • E. cayanensis: Nicora & Rúgolo de Agrasar (1987)
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’.