| # The grass genera of the world |

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

### Chasmopodium Stapf

Habit, vegetative morphology. Robust annual, or perennial (rarely). Culms 90–550 cm high; herbaceous; amply branched above. Leaves not basally aggregated; non-auriculate. Leaf blades broad; 5–40 mm wide; pseudopetiolate; without cross venation. Ligule present; 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 male-only, or hermaphrodite and sterile; homomorphic (except that the terminal spikelet is sometimes very long and thin).

Inflorescence. Inflorescence of cylindrical dorsiventral ‘racemes’, terminating the sparsely branching culms; spatheate; a complex of ‘partial inflorescences’ and intervening foliar organs (the ‘racemes’ distant from their spathes). Spikelet-bearing axes ‘racemes’; solitary, or paired; with substantial rachides; disarticulating; disarticulating at the joints. ‘Articles’ non-linear (narrowed at the base, concave at the apex, shorter than the spikelets); with a basal callus-knob; not appendaged; disarticulating transversely; somewhat hairy (ciliate on the back). Spikelets paired; secund (the axis dorsiventral, the sessile spikelets in two anterior rows and alternating, the pedicelled members posterior); sessile and pedicellate; consistently in ‘long-and-short’ combinations; in pedicellate/sessile combinations. Pedicels of the ‘pedicellate’ spikelets free of the rachis (stout). The ‘shorter’ spikelets hermaphrodite. The ‘longer’ spikelets male-only, or sterile.

Female-sterile spikelets. The pedicelled spikelet well developed. The lemmas awnless.

Female-fertile spikelets. Spikelets 6.3–7.5 mm long; compressed dorsiventrally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present (there being an annulus of hairs, above the disarticulation knob).

Glumes two; more or less equal; long relative to the adjacent lemmas; hairless; awnless; carinate (G2), or non-carinate (G1); G2 with the keel conspicuously winged (towards the top, the two keels of G1 also somehwat winged); very dissimilar (leathery or crustaceous, the G1 flat or concave dorsally, the G2 naviculate). Lower glume two-keeled; flattened on the back to concave on the back; not pitted; relatively smooth; seemingly many nerved. Upper glume seemingly many nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. The proximal incomplete florets 1; paleate. Palea of the proximal incomplete florets fully developed. The proximal incomplete florets male. The proximal lemmas awnless; 3 nerved; more or less equalling 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; pointed, or blunt; awnless; hairless; non-carinate; without a germination flap; 3 nerved. Palea present; relatively long; entire; awnless, without apical setae; not indurated; 2-nerved; keel-less. Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers not penicillate; without an apically prolonged connective. Ovary apically glabrous. Stigmas 2.

Fruit, embryo and seedling. Embryo large (about 4/5 the length of the caryopsis).

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Costal zones with short-cells. Costal short-cells conspicuously in long rows. Costal silica bodies present and well developed; ‘panicoid-type’; dumb-bell shaped.

Transverse section of leaf blade, physiology. C4 (‘bundles crowded’). Midrib conspicuous; with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups (between the vascular bundles).

Phytochemistry. Leaves without flavonoid sulphates (1 species).

Cytology. Chromosome base number, x = 8. 2n = 16.

Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Rottboelliinae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae; Rottboelliinae. 2 species.

Distribution, phytogeography, ecology. Tropical Africa.

References, etc. Leaf anatomical: Metcalfe 1960.

Special comments. Fruit data wanting.

Illustrations. • Chasmopodium caudatum: Hook. Ic. Pl. (1922). • Chasmopodium caudatum: Rose Innes, Ghana Grasses (1977).

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: 15th June 2025. delta-intkey.com’.

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