GRAMINEAE (GRASS FAMILY) 149 



61. TRIDENS R. & S. 



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

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

 subcoriaceous, convex below, bidentate, 3-nerved, the nerves silky-villous 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 dens, tooth.) TKIODIA R. Br. 



1. T. fULvus (L.) Hitchc. (TALL 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 ' ' a 



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



long, 5-8-flowered, on long pedicels ; glumes shorter than i^mma u'n oiled 



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



excurrent. (Poa 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 ; 

 spikt'le.ts about 5 mm. long, 6-8-flowered, nearly sessile ; glumes exceeding the 

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

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



62. TRfPLASIS 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 TpnrXdffios, thrice as many.) 



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, 6-8 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 

 south westw. Aug., Sept. Plant acid to the taste. FIG. 147. 



63. ERAGR6STIS 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. Annuals or perennials 

 with loose or dense terminal panicles. (Name from 1)p, spring, and Aypwru, a 

 grass. ) 



Annuals. 



Culms creeping ; plants polygamous 1. E. hypnoidet. 



Culms erect, ascending or decumbent ; flowers perfect. 

 Spikelets i-.VHdwered. 2-3 mm. long. 



Spikelets on lonjr capillary pedicels ; culms branched only at the base . 2. K. cnpillarit. 

 Spikelets on pedicels uot over 5 mm. long ; culms branched at the nudes 3. K. Frankii. 



