Ystia P. Compère
Named after Rd. Père Vanderyst (van der Yst), Belgian agrostologist.
Sometimes referred to 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; an unfringed membrane; short.
Reproductive organization. Plants bisexual, 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); spikelet-bearing axes 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. Ovary without a conspicuous apical appendage. Stigmas 2.
Taxonomy. Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae.
Distribution, ecology, phytogeography. 1 species; tropical Africa.
Paleotropical. African. Sudano-Angolan and West African Rainforest. Somalo-Ethiopian and South Tropical African.
References, etc. Morphological/taxonomic: Compère 1963.
Special comments. Fruit data wanting. Anatomical data wanting.
Cite this publication as: Watson, L., and Dallwitz, M. J. (1992 onwards). ‘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.’ http://biodiversity.uno.edu/delta/. Version: 18th August 1999. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993 onwards, 1998), and Watson and Dallwitz (1994), and Watson, Dallwitz, and Johnston (1986) should also be cited (see References).