MANUAL OF THE GRASSES OF THE UNITED STATES 



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distant, slender, flexuous, spreading 

 or drooping, 5 to 15 cm. long, nearly 

 simple, rather few-flowered; spikelets 

 on slender pedicels 1 to 10 mm. long, 

 oblong, mostly 6- to 10-flowered, 

 scarcely 5 mm. long; .glumes acumi- 

 nate; lemmas about 2 mm. long, ob- 

 tuse, obscurely pubescent along the 

 midnerve on the lower half, the mar- 

 gins pubescent, the midnerve min- 

 utely excurrent. % — Dry ground 

 among shrubs, Florida Keys, Texas, 

 Arizona, and northern Mexico; Cuba. 



10. Tridens flavus (L.) Hitchc. 

 Purpletop. (Fig. 284.) Culms erect, 

 tufted, 1 to 1.5 m. tall; basal sheaths 

 compressed-keeled; blades elongate, 

 3 to 10 mm. wide, very smooth; pan- 

 icle open, 15 to 35 cm. long, usually 

 purple or finally nearly black, rarely 

 yellowish, the branches distant, 

 spreading to drooping, naked below, 

 as much as 15 cm. long, with slender 

 divergent branchlets, the axils pubes- 

 cent, the axis, branches, branchlets, 

 and pedicels viscid; spikelets oblong, 

 mostly 6- to 8-flowered, 5 to 8 mm. 

 long; glumes subacute, mucronate; 

 lemmas 4 mm. long, obtuse, pubes- 

 cent on the callus and lower half of 

 keel and margins, the 3 nerves excur- 

 rent; palea a little shorter than the 

 lemma, somewhat bowed out below. 

 % (Tricuspis seslerioides Torr.) — 

 Old fields and open woods, New 

 Hampshire to Nebraska, south to 

 Florida and Texas. The type specimen 

 is the rare form with yellowish pan- 

 icle. In some Florida specimens the 

 excurrent nerves of the lemma are as 

 much as 1 mm. long. 



11. Tridens oklahomensis (Feath.) 

 Feath. (Fig. 285.) Culms 120 to 150 

 cm. tall, densely tufted, stout, erect, 

 more or less viscid, especially at and 

 below the nodes; blades to 60 cm. long 

 and 12 mm. wide, flat, glabrous or 

 sparsely pilose on the upper surface 

 at the base; panicles terminal and ax- 

 illary, purple, the terminal ones 20 to 

 25 cm. long, the long branches nar- 

 rowly ascending, floriferous nearly to 

 the base; spikelets 6 to 8 mm. long, 



Figure 282. — Tridens ambiguus. Panicle, X 1 ; floret, 

 X 5. (Curtiss 5020, Fla.) 



7- to 9-flowered, short-pediceled ; 

 glumes equal, acute, about 4 mm. 

 long; lowest lemma 4 mm. long. % 

 — Wet meadows, near Stillwater, 

 Okla. 



12. Tridens chapmani (Small) 

 Chase. (Fig. 286.) Culms 60 to 160 

 cm. tall, slender or occasionally rather 



Figure 283. — Tridens eragrostoides. Panicle, X 1; two 

 views of floret, X 5. (Swallen 1471, Tex.) 



coarse; lower leaves crowded toward 

 the base, the sheaths narrow, spread- 

 ing from the culm, keeled, glabrous, 

 densely villous on the collar; blades 

 flat or loosely rolled, elongate, atten- 

 uate, 3 to 7 mm. wide, narrowed 

 toward the base; panicles 15 to 25 

 cm. long, usually erect, the branches 



