The grass genera of the world

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

Pseudosorghum A. Camus

Habit, vegetative morphology. Erect or decumbent annual. Culms 40–100 cm high; herbaceous; branched above, or unbranched above. Culm internodes solid. Leaves not basally aggregated; non-auriculate. Leaf blades linear; narrow; 5–10 mm wide; without cross venation.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant (heterogamous); hermaphrodite and sterile, or hermaphrodite and sterile; overtly heteromorphic; in both homogamous and heterogamous combinations (the lowest pair of some or all racemes sterile).

Inflorescence. Inflorescence paniculate (all-sidedly branched, of few-to-many simple or branched spikelike racemes); contracted (relatively dense); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes ‘racemes’ (spiciform, peduncled); the spikelet-bearing axes with 4–5 spikelet-bearing ‘articles’ to with more than 10 spikelet-bearing ‘articles’ (few-to-many-jointed - the racemes fairly long, by contrast with Sorghum); with very slender rachides; disarticulating; disarticulating at the joints. ‘Articles’ linear; not appendaged; disarticulating transversely; densely long-hairy to somewhat hairy. Spikelets in triplets (a terminal triad), or paired (the rest); secund (all the pedicelled spikelets one one side); 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 hermaphrodite (except in lowest pair, where they may be male or sterile). The ‘longer’ spikelets male-only, or sterile.

Female-sterile spikelets. The basal barren spikelets lacking a palea.

Female-fertile spikelets. Spikelets 4–5.25 mm long; compressed dorsiventrally; falling with the glumes (with adjacent joint and pedicel). Rachilla terminated by a female-fertile floret. Hairy callus present (minute). Callus short; blunt.

Glumes two; more or less equal; long relative to the adjacent lemmas; glumes smooth, hairy or not; awnless; carinate (G2), or non-carinate (G1); very dissimilar (papery, the G1 truncate and 2-keeled, the G2 cymbiform and acute). Lower glume two-keeled; not pitted; relatively smooth; 9–13 nerved. Upper glume 7 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. The proximal incomplete florets 1; epaleate; sterile. The proximal lemmas awnless; 2 nerved; similar in texture to the female-fertile lemmas (thinly membranous); not becoming indurated.

Female-fertile florets 1. Lemmas less firm than the glumes; incised; 2 lobed; deeply cleft (to about halfway); awned. Awns 1; median; from a sinus; geniculate; hairless (ciliolate along margins); much longer than the body of the lemma. Lemmas hairy (long-ciliate); non-carinate; without a germination flap. Palea present (but absent in the barren basal spikelet); relatively long; awnless, without apical setae; not indurated. Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Cytology. 2n = 20.

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

Distribution, phytogeography, ecology. Indo-Malaysian.

Mesophytic; shade species and species of open habitats.

References, etc. Morphological/taxonomic: Camus 1920.

Special comments. Fruit data wanting. Anatomical data wanting. Illustrations. • P. zollingeri: Wu Zenghi, Flora Yunnanica 9 (2003)

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.’.