MANUAL OF THE GRASSES OF THE UNITED STATES 



477 



equal, 1-nerved, long-acuminate, mostly as long as the spikelet or 

 longer; lemmas bidentate, 3-nerved, the lateral nerves near the mar- 

 gin, the midnerve usually excurrent as a short awn, the margins 

 long-ciliate; palea broad, the nerves near the margin. Annuals or 

 perennials with simple panicles, the spikelets short-pediceled along 

 one side of the main branches. 

 Type species, Trichoneura hookeri 

 Anderss. Name from Greek thrix, 

 hair, and neuron, nerve, alluding 

 to the ciliate nerves of the f^ 

 lemma. 



1. Trichoneura elegans Swallen. 

 (Fig. 1025.) Annual, branching 

 at base; culms erect, rather ro- 

 bust, or ascending, 40 to 110 cm 

 tall, several-noded ; sheaths sca- 

 berulous; blades flat, or subinvo- 

 lute toward the tip, scabrous, 

 elongate, 3 to 7 mm wide; panicle 

 erect, 10 to 18 cm long, the axis 

 angled, scabrous; branches nu- 

 merous, stiffly ascending, the low- 

 er 5 to 8 cm long, rather densely 

 flowered; spikelets mostly 5- to 

 8-flowered, 9 to 10 mm long; 

 glumes about equaling the spike- 

 let, the setaceous tips slightly 

 spreading; lemmas scaberulous 

 toward the obtuse minutely lobed summit, the awn minute, the mar- 

 gins conspicuously ciliate on the lower half to two-thirds, the hairs 

 as much as 1 mm long, o — Sandy soil, southern Texas. 



92. TRIPOGON Roth 



Spikelets several-flowered, subsessile, appressed in two rows along 



one side of a slender rachis, the rachilla disarticulating above the 



glumes and between the florets; glumes some- 

 what unequal, acute or acuminate, narrow, 

 1-nerved; lemmas narrow, 3-nerved, bearing at 

 base a tuft of long hairs, the apex bifid, the 

 midnerve extending as a short awn. Our spe- 

 cies a low, tufted perennial, with capillary blades 

 and slender solitary spikes, the spikelets some- 

 what distant. Type species, Tripogon bromoides 

 Roth. Name from Greek treis, three, and 



pogon, beard, alluding to the hairs at the base of the three nerves 



of the lemma. 



1. Tripogon spicatus (Nees) Ekman. (Fig. 1026.) Culms 10 to 20 



cm tall; spike from one-fourth to half the entire height of the plant; 



spikelets 5 to 8 mm long. % — Rocky hills, central Texas, Mexico; 



Cuba; South America. 



Figure 1023. — Leptochloa panicoides. Panicle, X 1. 

 two views of floret, X 10. (Tracy 7451, Miss.) 



Figure 1024.— Distribution of 

 Leptochloa panicoides. 



