Trigonochloa P.M. Peterson & N. Snow. Ann. Bot. 109: 1327. 2012.

Snow, Neil & Peterson, Paul M., 2012, Systematics of Trigonochloa (Poaceae, Chloridoideae, Chlorideae), PhytoKeys 13, pp. 25-38 : 29

Trigonochloa P.M. Peterson & N. Snow. Ann. Bot. 109: 1327. 2012.

Type species:

Trigonochloa uniflora (Chipp.) P.M. Peterson & N. Snow.

Description.

Plants annual to short-lived perennial, sometimes rhizomatous or stoloniferou. Culms (15-)35-130 cm long, terete in cross section, solid, decumbent or clambering to erect; nodes glabrous. Leaf sheaths half as long to slightly longer than internodes, glabrous or ciliate apically along margins; ligules 1-3.5 mm long, membranous, irregularly lacerate with age; leaf blades 1-13(-17) cm long, 0.3-14(-19) mm wide, linear to broadly ovate, flat, typically thin and flaccid, apex acuminate to acute. Panicles17-55 cm long, 2.0-8 cm wide, exserted at maturity, open, narrowly oblong to narrowly elliptic, composed of several to numerous unilateral, secund spikes or spicate racemes scattered along a central axis; rachis semi-terete; branches (1.5-)2-7 cm long, ascending, straight or slightly drooping. Spikelets 1.9-2.8 mm long, 1 (rarely 2-flowered), laterally compressed, subsessile, overlapping; disarticulation above the glumes; glumes 1.8-3.1 mm long, subequal, as long or longer than the floret, subequal, linear to narrowly ovate, 1-nerved, apex acute to acuminate, muronate or emucronate; lemmas 1.2-2.6 mm long, ovate, 3-nerved, thinly membranous to hyaline, minutely hairy along the nerves, apex acute, entire, awnless; paleas 1.5-2.5 mm long, keels ciliolate. Stamens 3. Caryopses 1-1.2 mm long, narrowly elliptic, trigonous in cross section, narrowly but deeply sulcate on the hilar side; surface smooth to slightly rugose-striate, light brown, pericarp fused, tightly adherent to endosperm. 2 n = 36 for Trigonochloa uniflora ( Gould and Soderstrom 1974).

Comments.

An appropriate common generic name to differentiate Trigonochloa from other members of Leptochloa is "triangle-seed grass".

Key to species of Trigonochloa

1	Leaf blades 0.3-4.0 (-5.0) mm wide, more or less linear to narrowly ovate; leaf sheaths margins minutely ciliate towards the apex, the collar never pilose	Trigonochloa rupestris
-	Leaf blades 5-14 (-19) mm wide, ovate to broadly ovate; leaf sheaths glabrous or sparsely pilose near collar but not ciliate along upper margins	Trigonochloa uniflor a