The grass genera of the world
Including Balansochloa Kuntze, Sclerandrium Stapf & Hubbard
Habit, vegetative morphology. Annual, or perennial; stoloniferous (rarely), or caespitose. Culms 6–100 cm high; herbaceous; branched above, or unbranched above. The branching simple. Culm internodes hollow (or variable?). Leaves mostly basal, or not basally aggregated; non-auriculate. Leaf blades narrow; without cross venation. Ligule an unfringed membrane, or a fringed membrane (?); truncate; 0.5–2 mm long.
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, or female-only, male-only, and sterile. The male and female-fertile spikelets mixed in the inflorescence. The spikelets overtly heteromorphic (the sessile and involucral spikelets awnless, with dissimilar glumes); in both homogamous and heterogamous combinations (each raceme with one or two basal, homogamous pairs).
Inflorescence. Inflorescence peduncled, often long-exserted, solitary, capitate to elongate and consisting of few- to many-jointed racemes; digitate (the racemes appressed or divergent); espatheate (but the peduncle sometimes enclosed in the uppermost sheath); not comprising partial inflorescences and foliar organs. Spikelet-bearing axes very much reduced (to a peduncle, with two sessile spikelets and a pedicellate one on a short axis), or racemes; solitary, or paired to clustered (1–2(-6) racemes, fused at their bases); tardily disarticulating; finally disarticulating at the joints. Spikelets associated with bractiform involucres (the basal, sessile, homogamous spikelets forming an involucre round the heterogamous pairs); 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 male-only, or sterile (when involucral). The longer spikelets female-only.
Female-sterile spikelets. The sessile spikelet larger, male or barren, dorsally compressed. Male spikelets with 2 stamens in the upper floret. Rachilla of male spikelets terminated by a male floret. The male spikelets with glumes; with proximal incomplete florets; 2 floreted. The lemmas awnless. Male florets 2; (the upper floret) 2 staminate.
Female-fertile spikelets. Spikelets somewhat compressed dorsiventrally (subterete); falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present. The callus hairs brown (to yellow). Callus pointed, or blunt.
Glumes two; more or less equal; long relative to the adjacent lemmas; hairy, or hairless; pointed, or not pointed; awnless; non-carinate; similar (papery, narrow, blunt). Lower glume not two-keeled; not pitted; relatively smooth; 0–5 nerved. Upper glume 0–3 nerved. Spikelets with female-fertile florets only, or with incomplete florets (G. truncatiglumis). The incomplete florets when present, proximal to the female-fertile florets (sometimes suppressed). The proximal incomplete florets when present, 1; sterile. The proximal lemmas awnless.
Female-fertile florets 1. Lemmas without apical teeth, reduced to the membranous or stipitate awn-base; less firm than the glumes; entire; awned. Awns 1; median; apical; geniculate; hairy. Lemmas hairless; 1 nerved. Palea present; relatively long; entire, or apically notched, or deeply bifid; awnless, without apical setae; not indurated (hyaline); nerveless. Lodicules absent. Stamens 0. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small (0.6–3.2 mm long). Hilum short. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present. Intercostal papillae over-arching the stomata. Mid-intercostal long-cells having markedly sinuous walls. Microhairs present; panicoid-type. Stomata common. Subsidiaries papillate; triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies panicoid-type.
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; in simple fans, or associated with colourless mesophyll cells to form deeply-penetrating fans. Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures. Sclerenchyma all associated with vascular bundles.
Cytology. 2n = 14.
Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae; Germainiinae. 8 species.
Distribution, phytogeography, ecology. Asia, Malesia & North Australia.
References, etc. Morphological/taxonomic: Chaianan 1972. Leaf anatomical: this project.
Illustrations. • G. truncatiglumis: Gardner, 1952. • G. truncatiglumis, abaxial epidermis of leaf blade: this project. • G. truncatiglumis, abaxial epidermis of leaf blade: this project
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’.