GEAMINEAE (GRASS FAMILY) 



149 



61. TRIDENS R. & S. 



Spikelets .3-l?-flowered in open or strict panicles ; florets perfect or the upper- 

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

 subooriaoeous, convex below, bidentate, 3-nerved, the nerves silky-villous belovr 

 and at least the middle one extending in a muoronate point 

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

 — Perennials with long narrow leaves and terminjil panicles. 

 (Name from tres, three, and dms, tooth.) Tiuodia R. Br. 



1. T. flavus (L.) Hitohc. (Tail 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 panicles 

 2-4.5 dm. long, almost as wide, loose and open, the slender 

 branches spreading, naked below ; spikelets purple, 7-8 mm. 

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

 the lowest florets, mucronate ; the three nerves of the lemmas 

 excurrent. (Pua flava L. ; Triodia seslerioides Benth. ; T. cuprea Jacq.) — 

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



2. T. strictus (Nutt.) 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 excurrent. ( Triodia 

 striata Banth.) — Moist soil, s.e. Kan., and southw. July-Sept. 



HS. T. tiavus X 2. 

 Spikelet. 

 Same disijlayed. 

 Lemma UDrolIed. 



63. 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 rpiirXda-ios, thrice as many.) 



1. T. purpurea (Walt.) Chapra. (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 stifi 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 southw. ; 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. ERAGR6STIS Beauv. 



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

 rhaohilla 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 ; paleaa shorter than their lemmas, 

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

 with loose or dense terminal panicles. (Name from fjp, spring, and iypans, a 

 grass. ) 



Annuals. 



Culms creeping: ; plants polvpamous 1. E. hypnoidea, 



Cnlms erect, ascending or decinnbent; flowers perfect. 

 Spikelets 2-.')-flowerecl, 2-3 mm. lonf;;. 

 Spikelets on Innff capillary pedicels ; culms branched only at the base . 2. E. cnpillaria. 

 Spikelets on pedicels not over 5 mm. long ; culraR branched at the nodes 3. E. Frankii. 



