The grass genera of the world
Habit, vegetative morphology. Perennial; caespitose. The flowering culms leafy. Culms 100–200 cm high; herbaceous; unbranched above. Culm nodes hidden by leaf sheaths. Culm leaves present. Culm internodes hollow. Plants unarmed. Leaves not basally aggregated; auriculate (on the sheath); without auricular setae. Leaf blades lanceolate, or elliptic; broad; 30–50 mm wide (and large); not cordate, not sagittate; flat; pseudopetiolate (narrowed to the base); cross veined; persistent. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence of spicate main branches (in a terminal racemose panicle, about 40 cm long); espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes spikes; persistent. Spikelets solitary; secund; biseriate (on two sides of the slender, 3-sided axis); pedicellate.
Female-fertile spikelets. Spikelets about 5 mm long; adaxial; strongly compressed laterally; falling with the glumes; with a distinctly elongated rachilla internode between the glumes, with a distinctly elongated rachilla internode above the glumes, and with distinctly elongated rachilla internodes between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets. Hairy callus present.
Glumes two; very unequal (by elongation of the internode between them, the G1 and G2 being actually about the same length); shorter than the spikelets; shorter than the adjacent lemmas; dorsiventral to the rachis; hairless; glabrous (scabrous on the midvein); awned (the median nerve excurrent as a short subule); carinate; similar (membranous). Lower glume shorter than the lowest lemma; 5 nerved. Upper glume 3–5 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets 1, or 2; merely underdeveloped; awned.
Female-fertile florets 1. Lemmas ovate; similar in texture to the glumes to decidedly firmer than the glumes (papery); not becoming indurated; minutely incised, or entire; when detectably incised, minutely 2 lobed; not deeply cleft; awned. Awns 1; median; from a sinus, or dorsal to apical; from near the top (from just behind the apex or minute sinus - i.e. subapical); non-geniculate; flexuous; hairless (antrorsely scaberulous); much shorter than the body of the lemma to about as long as the body of the lemma; entered by one vein. Awn bases not twisted; not flattened. Lemmas hairless; glabrous; carinate; having the margins lying flat on the palea; weakly 3–5 nerved; with the nerves non-confluent. Palea present; relatively long; tightly clasped by the lemma; apically notched (minutely); awnless, without apical setae; thinner than the lemma to textured like the lemma; not indurated; 2-nerved; 2-keeled. Palea back glabrous. Palea keels winged; scabrous. Lodicules present; 2; joined (represented by a single, anterior structure); glabrous. Stamens 2. Anthers not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit small (2–4 mm long). Hilum short. Pericarp thin. Embryo small.
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 (of medium thickness). Mid-intercostal long-cells rectangular; having markedly sinuous walls (the sinuosity fairly coarse and irregular). Microhairs present; elongated; clearly two-celled; panicoid-type. Stomata common. Subsidiaries non-papillate; low dome-shaped to triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies irregularly cross-shaped. No macrohairs or prickles seen. Costal zones with short-cells. Costal short-cells conspicuously in long rows. Costal silica bodies present and well developed; panicoid-type; cross shaped (a few), or dumb-bell shaped (mostly, short to elongated), or nodular (a few).
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; with adaxial palisade; without arm cells; with fusoids. The fusoids an integral part of the PBS (seemingly, in places), or external to the PBS (definitely, in places). Leaf blade adaxially flat. Midrib conspicuous (via its massive abaxial keel, heavy sclerenchyma and conspicuous lacunae); having a conventional arc of bundles (the bundles separated by lacunae); with colourless mesophyll adaxially (and with lacunae). The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups; in simple fans (these large and wide). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures (most bundles with a small I or T). Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Centothecoideae; Centotheceae. Soreng et al. (2015): Panicoideae; Zeugiteae. 2 species.
Distribution, phytogeography, ecology. Congo.
Shade species; glycophytic. Forests.
References, etc. Leaf anatomical: Jacques-Félix 1962; this project.
Illustrations. • C. dewildemanii: Jacques-Félix, 1962. • Inflorescence detail and a spikelet (C. dewildemanii)
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’.