ORDER 155. GRAMINE^E. 



389 



c Awns about equal, spreading. Lower gl. longer than the upper Nos. 5 7 



Glumes equal, or the lower shorter. ...Nos. 8, 9 



1 A. tuberculosa N. Culm rigid, 820', with tubercles in the axils of the numerous 



branches; pan. large and loose; glume linear, awned, 1'; triple awn (d) 2', united 

 half-way up, thence involved and spreading. (T) Mountains, N. J., and W. 



2 A. dlchotoma MX. (a) Culm 8 12', dichotomottsbj branched; gl. 34"; lateral 



awns erect, minute, the middle awn (6) as long as the pale (3"), twice bent to the 

 form of a bayonet. (T) Dry sandy fields : common. 



3 A. ramosissima Engelm. Culms diffusely branched; gl. 9 10", awn-pointed ; 



lateral awns 2 1 , middle awn 1', spreading. (I) Sands, 111., Ky. 



4 A. griifilis E.I. Very slender, i Iff; pan. virgatc, 4 8'; glume and flower equal, 



(2| 3"); middle awn 910", horizontal, the lateral erect. @ Sandy places. 

 /3. tirsrata. Taller (2 3f), pan. If ; gl. and fl. shorter (2"). S. (Chapman). 



5 A. lanata Poir. Culms 2 4f, stout, branched from base; Ivs. flat, with woolly 



fheaths ; pan. 1 2f, woolly in its axils ; upper glume, lower (purplish) pale and lat- 

 eral awns each 4 5", middle awn some longer. ii Sandy soils, S. 



6 A. spicifirmis Ell. Culms 1 3f, rigid, simple; Ivs. rolled, rigid, smooth; pan. 



rpike-form, dense ; flower 1' long, awns as long. gl. much shorter, u Wet sands, S. 



7 A. purpiirascens Poir. (c) Culms slender, 2 3f; Ivs. scarcely rolled ; pan. If 



long, loosely spicate ; glume and fl. 4 5", purplish ; awns 1', spreading. Of Sandy. 



8 A. stricta MX. Culms 2 3f, strictly erect, with long rigid rolled Ivs.; pan. loosely 



racemous, If; gl. 67", fl. 6", lateral awns 79", central 915". y. Va., and S. 



9 A. oligantha MX. Culms 11 Jf, in tufts ; raceme few-flowered; glume and fl. 9", 



very slender, awns capillary, divaricate, 18 30" long. Prairies, W. and S. 



17. PASPALUM, L. Spikelets piano con- 

 vex, in one-sided spikes. Glumes (apparently) 

 2, membranous, equal, ovate or orbicular, closely 

 applied to the fertile flower. Grain coated 'with 

 the smooth coriaceous pales. (But theoretically, 

 the lower glume is obsolete, and its place sup- 

 plied by the empty pale of an abortive flower. 

 In Nos. 15 17 the lower glume appears, under a 

 lens, as a mere rudiment.) Spikes linear, the 

 flowers in 2 4 rows. 



PASPALUM. Spikelets round or round-oval, obtuse. 



Spikes alternate... (*) 

 DIGITARIA. Spikelets ovate to lanceolate, acute. 



Spike? often digitate. . .(**) 



* Terminal spike mostly solitary, rarely 2, \" wide, long-stalked . . No. 1 



* Terminal spikes mostly 3 or 4, 2" wide. Spikelets in 2 rows Nos. 2, 3 



* Terminal spikes mostly 4 or 5. Spikelets close, in 3 or 4 rows Nos. 46 



Spikelets in remote pairs No. 7 



** Rachis lenf-like, broader than the spikelets. Spikes alternate Nos. 3, 9 



** Rachis narrower than the spikelets. Spikes digitate. . .(a) 



a Glumes (gl. and pale) about equal, as long as the flower. . .(ft) 



a Ols. (both conspicuous) one or both very short. Spks. 49 Nos. 16, 17 



b Spikes spreading, always two in Nos. 10, 11 ; two six in No. 12 



b Spikes erect. Rachis fiat, spikelets by I's or"2's, close Nos. 13, 14 



Rachis filiform, spikelets by 3's, loose No. 15 



1 P. setaceum MX. Culm slender, ascending, 1 2f, naked above ; Ivs. linear, flat, 

 23" wide, soft, hairy; spikes very slender, 24', 1 or 2 on the long peduncle, often 



