The grass genera of the world
Habit, vegetative morphology. Annual. Culms 30 cm high; herbaceous; branched above. Leaves not basally aggregated; non-auriculate. Leaf blades linear (broadly); narrow; 3–7 mm wide (to 5 cm long); flat; without cross venation; persistent. Ligule an unfringed membrane; truncate (erose). Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality.
Inflorescence. Inflorescence a false spike, with spikelets on contracted axes (a spike bearing 2–3 little ovate pseudo-racemes, at the summit of the culm). Primary inflorescence branches 2–3 (i.e., the glomerules or pseudo-racemes). Rachides of the pseudoracemes broadly winged (the wings enfolding the several spikelets and their associated spiny involucres). Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes very much reduced (to pseudo-racemes); disarticulating; falling entire (the pseudo-racemes falling). Spikelets associated with bractiform involucres (each spikelet subtended and partly invested by a rigid, branched, spiny bract or involucre). The involucres shed with the fertile spikelets (i.e., as part of the pseudo-raceme complex). Spikelets secund (i.e., the spikelets on one side of the spikelet-bearing branch).
Female-fertile spikelets. Spikelets morphologically conventional (in the last analysis); 5.5–6 mm long; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes two; relatively large; very unequal (G1 about half length of G2, and hyaline); shorter than the adjacent lemmas; hairless (G2 scaberulous); pointed; awnless; non-carinate. Lower glume 0 nerved. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; epaleate (?); sterile. The proximal lemmas awnless; more or less equalling the female-fertile lemmas; less firm than the female-fertile lemmas (herbaceous); not becoming indurated.
Female-fertile florets 1. Lemmas similar in texture to the glumes to decidedly firmer than the glumes (leathery, whitish); not becoming indurated; entire; pointed; awnless; hairless; non-carinate; having the margins lying flat on the palea (seemingly). Palea present; relatively long; entire; awnless, without apical setae; not indurated. Stamens 3. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit small (2.5 mm long); compressed dorsiventrally. Hilum short. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals much narrower); of similar wall thickness costally and intercostally (rather thin walled). Intercostal zones with typical long-cells. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type; 36–48 microns long; 6 microns wide at the septum. Microhair total length/width at septum 7. Microhair apical cells 21–27 microns long. Microhair apical cell/total length ratio 0.53–0.67. Stomata common; 24–30 microns long. Subsidiaries dome-shaped (mostly), or triangular (in a few files). Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare (very scarce); (the few seen) not paired (solitary); not silicified. Small prickles numerous. Costal short-cells conspicuously in long rows. Costal silica bodies panicoid-type; cross shaped, butterfly shaped, and dumb-bell shaped (short).
Transverse section of leaf blade, physiology. C4; XyMS. Leaf blade adaxially flat. Midrib conspicuous (via its small keel, and adaxial colourless tissue); with one bundle only to having a conventional arc of bundles (depending on whether it is taken to include the small laterals flanking the median); with colourless mesophyll adaxially. Bulliforms not present in discrete, regular adaxial groups (the adaxial epidermis extensively bulliform). Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders absent (with relatively little sclerenchyma, save for adaxial and abaxial strands). Sclerenchyma all associated with vascular bundles.
Special diagnostic feature. The inflorescence not as in Odontelytrum (q.v.).
Cytology. Chromosome base number, x = 9. 2n = 18 (+ 3B).
Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paniceae; Anthephorinae. 1 species (C. cryptacanthum).
Distribution, phytogeography, ecology. Tanzania.
In dry bushland; species of open habitats. Bushland.
References, etc. Morphological/taxonomic: Clayton 1970. Leaf anatomical: 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’.