Family: Poaceae |
Jesús Valdés-Reyna Plants perennial; usually cespitose, often with short, knotty rhizomes, occasionally with elongate rhizomes, never stoloniferous. Culms 5-180 cm, erect, mostly glabrous, lower nodes sometimes with hairs. Sheaths shorter than the internodes, open; ligules membranous and ciliate or of hairs; blades 6-25 cm long, 1-8 mm wide, flat or involute, margins not thick and cartilaginous. Inflorescences terminal, usually panicles (sometimes reduced to racemes), 5-40 cm, exceeding the upper leaves, exserted. Spikelets 4-10(13) mm, laterally compressed, with 4-11(16) florets, more than 1 floret bisexual; sterile florets distal to the fertile spikelets; disarticulation above the glumes. Glumes usually from shorter than to equaling the distal florets, sometimes longer; lower glumes 1(3)-veined; upper glumes about equal to or longer than the lower glumes, 1-3(9)-veined, unawned; calluses usually glabrous, sometimes pilose; lemmashyaline or membranous, 3-veined, veins usually shortly hairy below, apices rounded to truncate, emarginate to bilobed, midvein often excurrent to 0.5 mm, lateral veins not or more shortly excurrent; paleas glabrous or shortly pubescent on the lower back and margins, veins glabrous or ciliolate; lodicules 2, free or adnate to the palea; anthers 3, reddish-purple. Caryopses dorsiventrally compressed and reniform in cross section, dark brown; embryos about 2/5 as long as the caryopses. x = 10. Name from the Latin tres, three, and dens, tooth, referring to the three shortly excurrent veins of Tridens flavus, the type species. 2020-10-26: Description of glume lengths corrected, thanks to information sent by Art Gibson. SELECTED REFERENCES Burbidge, N.T. 1953. The genus Triodia R. Br. (Gramineae). Austral. J. Bot. 1:121-184; Gould, F.W. 1975. The grasses of Texas. Texas A&M University Press, College Station, Texas, U.S.A. 653 pp.; Hitchcock, A.S.1951 [title page 1950]. Manual of the Grasses of the United States, ed. 2, rev. A. Chase. U.S.D.A. Miscellaneous Publication No. 200. U.S. Government Printing Office, Washington, D.C., U.S.A. 1051 pp.; Tateoka, T. 1961. A biosystematic study of Tridens(Gramineae). Amer. J. Bot. 48:565-573. |