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The grass genera of the world

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

Ystia P. Compère

Named after Rd. Père Vanderyst (van der Yst), Belgian agrostologist.

~ Schizachyrium (S. kwiluense)

Habit, vegetative morphology. Perennial. Culms about 50–150 cm high; herbaceous; branched above. Leaves not basally aggregated. Leaf blades narrowly linear; narrow; without cross venation. Ligule an unfringed membrane; short.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality; overtly heteromorphic (the pedicellate spikelets with awns reduced or lacking).

Inflorescence. Inflorescence paniculate (a false panicle of small ‘racemes’); spatheate; a complex of ‘partial inflorescences’ and intervening foliar organs. Spikelet-bearing axes ‘racemes’; the spikelet-bearing axes with 6–10 spikelet-bearing ‘articles’ (with 6–7 spikelet pairs); solitary (in the spatheoles); with very slender rachides (flexuose); disarticulating; disarticulating at the joints. ‘Articles’ scabrid. Spikelets paired and in triplets (with terminal triad); 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. The ‘longer’ spikelets hermaphrodite.

Female-fertile spikelets. Spikelets 4–5 mm long; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present. Callus short; blunt.

Glumes present; two; long relative to the adjacent lemmas; hairless (glabrous below, scabrid above); awnless; very dissimilar (the G1 papery with involute margins and apically bidentate, the G2 thinner, naviculate, shortly subulate or acuminate). Lower glume not two-keeled (except at the tip); not pitted; relatively smooth; (5–)7(–9) 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 (reduced to a hyaline lemma); sterile. The proximal lemmas awnless.

Female-fertile florets 1. Lemmas less firm than the glumes (hyaline); not becoming indurated; incised; deeply cleft (to about a third); awned (in the sessile spikelet), or awnless to mucronate (in the pedicellate spikelet). Awns 1; median; from a sinus; geniculate; shortly hairy, or hairless (scabrid); about as long as the body of the lemma to much longer than the body of the lemma (4–5 mm long, in the sessile spikelet). Lemmas non-carinate; without a germination flap. Palea absent. Lodicules present; 2; fleshy. Stamens 3. Stigmas 2.

Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae. Soreng et al. (2015): Panicoideae (as a synonym?); Andropogonodae; Andropogoneae; Andropogoninae. 1 species.

Distribution, phytogeography, ecology. Tropical Africa.

References, etc. Morphological/taxonomic: Compère 1963.

Special comments. Fruit data wanting. Anatomical data wanting.


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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’.

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