MANUAL OF THE GRASSES OF THE UNITED STATES 



781 



let about 1 cm. long, the first glume 

 papillose-hispid toward the tip and 

 margins, sometimes nearly glabrous. 

 01 — Rocky hills and canyons, 

 Texas to Arizona; tropical and warm- 

 er regions of both hemispheres. 



2. Heteropogon melanocarpus (Ell. ) 

 Benth. Sweet tanglehead. (Fig. 

 1183.) Plants annual, 1 to 2 m. tall, 

 freely branching; sheaths smooth, the 

 upper part of the keel, especially of 

 the upper sheaths, with a row of 

 concave glands; blades 5 to 10 mm. 

 wide; raceme 3 to 6 cm. long; looser 

 than in H. contortus; sessile spikelets 

 9 to 10 mm. long, relatively thick, the 

 awns 10 to 15 cm. long; pedicellate 

 spikelet 1.5 to 2.5 cm. long, the first 

 glume with a line of punctate glands 

 along the middle. O — Pine woods, 

 fields, and waste places, Georgia, 

 Florida, and Alabama; Arizona; 

 tropical regions of both hemispheres. 

 The plant when fresh emits an odor 

 like that of citronella oil. 



160. TRACHYPOGON Nees 



Spikelets in pairs, along a slender 

 continuous rachis, one nearly sessile, 

 staminate, awnless, the other ped- 

 icellate, perfect, long-awned; the ped- 

 icel of the perfect spikelet obliquely 

 disarticulating near the base, forming 

 a sharp-barbed callus below the 

 spikelet; first glume firm-membra- 

 naceous, rounded on the back, several- 

 nerved, obtuse; second glume firm, 

 obscurely nerved; fertile lemma nar- 

 row, extending into a stout twisted 

 and bent or flexuous awn; palea 

 obsolete; sessile spikelet persistent, as 

 large as the fertile spikelet and 

 similar but awnless. Perennial, moder- 

 ately tall grasses, with terminal 

 spikelike solitary or fascicled ra- 

 cemes. Type species, Trachypogon 

 montufari. Name from Greek trachus, 



Figure 1183. — Heteropogon melanocarpus, X 1 

 (Fredholm 6405, Fla.) 



rough, and pogon, beard, alluding to 

 the plumose awn of the fertile spike- 

 let. 



1. Trachypogon secundus (Presl) 

 Scribn. Crinkle-awn. (Fig. 1184.) 

 Culms tufted erect, slender, 60 to 

 120 cm. tall, the nodes appressed 

 hirsute; sheaths with erect auricles 

 2 to 5 mm. long; blades flat to sub- 

 involute, 3 to 8 mm. wide; raceme 

 solitary, 10 to 18 cm. long, the rachis 

 glabrous; spikelets 6 to 8 mm. long, 

 pubescent, the awns of perfect spike- 

 lets 4 to 6 cm. long, short-plumose 

 below, nearly glabrous toward the 

 tip. % (Included in T. montufari 

 (H. B. K.) Nees in the Manual, 

 ed. 1.) — Rocky hills and canyons, 

 southern Texas, southwestern New 

 Mexico, and southern Arizona; Mex- 

 ico to Argentina. 



161. ELYONURUS Humb. and Bonpl. ex Willd. 



Spikelets in pairs along a somewhat tardily disarticulating rachis, the 

 joints and pedicels short, thickened, and parallel, the sessile spikelets perfect, 

 appressed to the concave side, the pedicellate spikelet staminate, similar to the 

 sessile one, both awnless, the pair fa) ling with a joint of the rachis; first glume 



