Family: Poaceae |
Thomas F. Daniel Plants usually perennial, rarely winter annuals; usually cespitose, sometimes the culms solitary. Culms (5)20–130 cm, leaves evenly distributed. Sheaths open; auricles absent; ligules membranous, erose; blades flat or involute, glabrous or pubescent. Inflorescences panicles, open or contracted, nodding to erect; disarticulation below the glumes, the distal floret sometimes disarticulating first. Spikelets pedicellate, 2.1–9.5 mm, laterally compressed, with 2–3 florets; rachillas glabrous or pubescent, prolonged beyond the base of the distal floret as a slender bristle. Glumes almost equaling the lowest floret, dissimilar in width, membranous to subcoriaceous, margins scarious, apices unawned; lower glumes narrower than the upper glumes, 1(3)-veined, strongly keeled, apices acute; upper glumes elliptical to oblanceolate, obovate, or subcucullate, 3(5)-veined, strongly to slightly keeled, apices acuminate, acute, rounded, or truncate; calluses glabrous; lemmas herbaceous, not indurate, rounded on the lower back, smooth or partly or wholly scabrous, usually keeled near the apices, 3(5)-veined, veins usually not visible, unawned or awned from just below the apices, awns straight or geniculate; paleas hyaline, shorter than the lemmas; lodicules 2, free, membranous, glabrous, toothed or entire; anthers 3; ovariesglabrous. Caryopses shorter than the lemmas, concealed at maturity, linear-ellipsoid, glabrous; endosperm liquid. x = 7. Name from the Greek sphen, ‘wedge’, and pholis, ‘scale’, in reference to the upper glumes. Sphenopholis includes six species, all of which are native to the Flora region. Its greatest diversity is in the southeastern United States. One species, Sphenopholis obtusata, extends outside the region to southern Mexico and the Caribbean. It has also been collected in Hawaii, but is not known to be established there. Interspecific hybridization is known in the genus, but intermediate plants are not frequently encountered. Trisetum interruptumBuckl. is sometimes treated in Sphenopholis (e.g., Finot et al. 2004) because its spikelets disarticulate below the glumes. Glume widths are measured in side view, from the lateral margin to the midvein. SELECTED REFERENCES Erdman, K.S. 1965. Taxonomy of the genus Sphenopholis (Gramineae). Iowa State Coll. J. Sci. 39:289–336; Finot, V.L., P.M. Peterson, R.J. Soreng, and F.O. Zuloaga. 2004. A revision of Trisetum, Peyritscia, and Sphenopholis (Poaceae: Pooideae: Aveninae) in Mexico and Central America. Ann. Missouri Bot. Gard. 91:1–30;Smith, E.B. (ed.). 1991. An Atlas and Annotated List of the Vascular Plants of Arkansas, ed. 2. Edwin B. Smith, Fayetteville, Arkansas, U.S.A. 489 pp. |