GRAMINEAE (GRASS FAMILY) 



149. 



61. TRIDENS R. & S. . 



Spikelets 3-12-flowered in open or strict panicles ; florets perfect or the upper- 

 most staminate ; glumes unequal, keeled, shorter than the spikelet ; lemma 

 subcoriaceous, convex below, bidentate, 3-nerved. the nerves silky-viilous below 

 and at least the middle one extending in a mucronate point 

 between the teeth ; palea broad, the nerves nearly marginal. 

 — Perennials with long narrow leaves and terminal panicles. 

 (Name from tres, three, and dt^ns. tooth.) Tkiudia K. Br. 



1. T. flavus (L.) Hitchc. (1 all Red Top.) Culms erect, 

 1-2 m. high, viscid in the axis of the panicle and below it ; 

 sheaths bearded at the summit, otherwise glabrous as are the 

 long flat or involute tapering blades ; the showy panicJes 

 2r-i.b dm. long, almost as wide, loose and ope7i, the slender 

 branches spreading^ naked below; spikelets prii'ple. 7-8 mm. 

 long, 5-8-flowered, on long pedicels ; glumes shorter than 

 the lowest florets., imicronate ; the three nerves of the lemmas 

 excurrent. (Poa flava L. ; Tinodia seslerioides Benth. ; T. cv.prea Jacq.) — 

 Dry or sandy fields. Ct. to Mo., and south w, Aug.. Sept. Fig. 146. 



2. T. strictus (Xutt.) Nash. Caespitose. 12-14 dm. high ; culms stout, erect; 

 leaves long and rigid : panicle pale or purplish, dense and spike-like, 1-3 dm. long ; 

 spikelets about 5 mm. long, 5-8-flowered, nearly sessile ; glumes exceeding the 

 lower florets, mucronate ; only the midnerve of the lemma excirrrent. (Triodia 

 stricta Benth.) — Moist soil, s.e. Kan., and southw. July-Sept. 



140. T. tiavus X 2. 

 Spikelet. 

 Same displayed, 

 lemma unrolled. 



62. TRIPLASIS Beauv. 



Spikelets 3-6-flowered, the florets remote, the lowest stipitate, perfect or the 

 uppermost staminate ; glumes unequal, keeled, shorter than the florets ; lemmas 

 2-cleft, the 3 nerves strongly ciliate, the midnerve excurrent as a short awn 



between the lobes ; palea shorter, broad, the nerves nearly 

 marginal and densely long-ciliate from the middle to the 

 apex. — Perennials with small nearly simple panicles. (Name 

 from TpLirXdcnos, thrice as iiiany.) 



1. T. purpurea (Walt.) Chapm. (Sand Grass.) Culms 

 tufted, widely spreading or ascending, wiry. 3-8 dm. long, 

 nodes bearded ; sheaths and the small rigid blades scabrous ; 

 terminal panicles 3-7 cm. long, the few stiff branches finally 

 divergent; smaller panicles (partially hidden in the sheaths) 

 produced at the nodes late in the season ; spikelets short- 

 pediceled, usually rose-purple, 5-8 mm. long; the awn of the lemma scarcely 

 exceeding the truncate lobes. {Tricuspis Gray; Triodia Hack.) — In sand, 

 Me. to Va., along the coast, and Bouthw. ; also along the Great Lakes and 

 southwestw. Aug., Sept. — Plant acid to the taste. Fig. 147. 



147. T. purpurea x 2 

 Spikelet and lemma. 



63. ERAGROSTIS Beauv. 



Spikelets strongly compressed, 3-many-flowered ; the uppermost floret sterile ; 

 rhachilla articulated but sometimes not disjointing until after the fall of the 

 glumes and lemmas with the grain ; glumes keeled, much shorter than the 

 spikelets ; lemmas 3-nerved, broad, keeled ; paleas shorter than their lemmas, 

 often persistent after their fall, the strong nerves ciliate. Animals or perennials 

 with loose or dense terminal panicles. (Name from fjp^ spring, and k^pwris. a 

 grass.) 



1. E. hypnoideis. 



Annuals. 



Culms creeping-; plants polygamous 



Culms erect, ascendinj;: or decumbent; flowers perfect. 

 Spikelets '2-5-flowered. 2-8 mm. long. 

 Spikelets on lonsr capillary pedicels ; culms branched only at tlie base . 2. E. ca pi/tans. 

 Spikelets on pedicels not over 5 mm. long ; culm-: brauched at the nodes 3. £'. Frankii. 



