Plants annual and tufted or perennial and occasionally rhizomatous. Culms
14-100 cm, usually ascending; internodes glabrous. Ligules to
1 mm, of hairs; blades 1-5 mm wide, flat or involute, hispid or
with papillose-based hairs. Panicles 3-7 cm long, 1-6 cm wide. Spikelets 6.5-9
mm, with 3-4 florets. Glumes about 2 mm, glabrous or scabrous,
apices erose; lemmas
3-4 mm, lobes shorter than 1 mm, rounded; awns shorter than 2 mm,
straight;
paleas about 2.5 mm, keels ciliate; anthers about 2 mm, reddish-purple.
Caryopses about 2 mm long, 0.6 mm wide, tapering distally, tan.
2n
= 40.
Triplasis purpurea grows in sandy soils throughout the eastern and
central portion of the Flora region, extending southward through
Mexico to Costa Rica. It is far more common in maritime dunes than T.
americana.
Plants in the Flora region belong to Triplasis purpurea (Walter)
Chapm. var. purpurea.
Slender annual 2-8 dm; blades 1-2 mm wide, shorter than their sheaths, the upper much reduced; terminal infl 2-8 cm, with a few branches each bearing a few 2-5-fld purple spikelets; glumes narrowly lanceolate, 2-4 mm; lemmas 3-4 mm, the short lobes rounded or erose, the hairy awn 1 cm or less; rachilla-joints half as long as the lemma; included panicles and solitary spikelets produced within the lower sheaths. Dry sand along the coast from N.H. to Tex.; also along the shores of the Great Lakes, and in the interior from Ind. to Minn., Colo., and Tex.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.