The grass genera of the world
Habit, vegetative morphology. Perennial; densely caespitose. The flowering culms leafy. Culms about 10–25 cm high (?); herbaceous; unbranched above. Rhizomes pachymorph. Plants unarmed. Leaves not basally aggregated; without auricular setae. Leaf blades broad; 12–20 mm wide (4–7.5 cm long, acute); not cordate, not sagittate (sub-truncate and slightly asymmetrical at base); pseudopetiolate.
Reproductive organization. Plants monoecious with all the fertile spikelets unisexual; without hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; female-only and male-only. The male and female-fertile spikelets mixed in the inflorescence (each panicle with a few female spikelets, each accompanied by 1–2 males). The spikelets overtly heteromorphic; all in heterogamous combinations.
Inflorescence. Inflorescence indeterminate (a synflorescence); of reduced axillary and terminal racemelike panicles; a complex of partial inflorescences and intervening foliar organs. Spikelet-bearing axes persistent. Spikelets paired, or in triplets; not secund (?); pedicellate; consistently in long-and-short combinations; in pedicellate/sessile combinations (each female with 1–2 males). The shorter spikelets male-only. The longer spikelets female-only.
Female-sterile spikelets. Male spikelets 3 mm long, without glumes, lemma thin and 3-nerved, stamens 3. Rachilla of male spikelets terminated by a male floret. The male spikelets without glumes; without proximal incomplete florets; 1 floreted. Male florets 1; 3 staminate.
Female-fertile spikelets. Spikelets about 6 mm long; lanceolate; compressed dorsiventrally; disarticulating above the glumes; with conventional internode spacings. Rachilla terminated by a female-fertile floret. Callus absent.
Glumes two; pointed (acuminate to attenuate); non-carinate; similar (leathery). Lower glume 3 nerved. Upper glume 3 nerved. Spikelets with female-fertile florets only.
Female-fertile florets 1. Lemmas becoming mottled with purple; becoming indurated (presumably); awnless; hairless; non-carinate; 3 nerved (the nerves white - according to Swallen), or 5 nerved (Calderón & Soderstrom). Palea present; indurated (presumably). Stamens 0. Stigmas 2 (with long processes, plumose, not curling).
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; costal and intercostal (but largely absent from the mid-intercostal regions). Intercostal papillae over-arching the stomata; several per cell (small, circular, numerous, in rows on the costal long-cells, scattered over the intercostals bordering the costae, and concentrated in rings around the stomatal crypts). Long-cells markedly different in shape costally and intercostally (the costals much narrower); of similar wall thickness costally and intercostally to differing markedly in wall thickness costally and intercostally (the costals thicker walled in places). Mid-intercostal long-cells rectangular; having markedly sinuous walls (the sinuosity coarse, fairly irregular). Microhairs present; elongated; clearly two-celled; panicoid-type. Stomata common. Subsidiaries papillate (two per cell, overlying the guard-cells); dome-shaped and triangular. Guard-cells seemingly overlapped by the interstomatals (the stomata in depressions between the interstomatals, overhung by the small papillae). Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies crescentic, tall-and-narrow, cross-shaped, and vertically elongated-nodular (mainly a slim version of the latter). With numerous intercostal prickles. Costal short-cells conspicuously in long rows (over the main veins), or predominantly paired (over minor veins). Costal silica bodies present and well developed; panicoid-type; cross shaped to dumb-bell shaped (large); sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with arm cells; with fusoids. The fusoids external to the PBS. Leaf blade adaxially flat. Midrib conspicuous; having a conventional arc of bundles (a large median, with a small bundle on each side); with colourless mesophyll adaxially. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups; in simple fans (these wide, of large cells). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles save the median); forming figures (Is or anchors, in places). Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Bambusoideae; Oryzodae; Olyreae. Soreng et al. (2015): Bambusoideae; Bambusodae; Olyreae; Olyrinae. 1 species (R. smithii).
Distribution, phytogeography, ecology. Brazil.
References, etc. Morphological/taxonomic: Swallen 1956. Leaf anatomical: studied by us.
Special comments. Fruit data wanting.
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’.