72 TRIANDRIA.— DIGYNIA. 



96. SETARIA. 

 I, S. viridis: spike cylindrical ; involucrum of 4 — 10 

 fasciculate bristles, scabrous upward; spikelets 

 geminate ; perfect floret smooth ; sheaths pubescent. 



HAB. Cultivated grounds. July — Aug. H. Culm \\ 

 ft. high, simp. ; leav. smooth ; invoL longer than 

 theft, 

 I. S. glauca: spike cylindrical: involucrum of many fas- 

 cicled bristles, scabrous upward ; perfect floret 

 transversely rugose. 



HAB. Fields and cultivated grounds. July — Aug. 0. 

 Culm 2 ft. high ; invoL yellow when old. 



/3. purpurascens : sheaths hairy ; glumes and bristles 

 of the involucrum purple. 

 ). S. verticillata : spike subverticillate ; bristles of the 

 involucrum 2, retrorsely scabrous ; spikelets soli- 

 tary ; corolla of the perfect floret nearly smooth. 



HAB. Sandy cultivated grounds. July. 0. Culm 

 18 in, high, smooth; spike 2 in. long ; rach. hispid ; 

 invol. purplish. 

 }. S. italica : spike compound, interrupted at the base, 

 nodding ; spikelets conglomerate ; involucrum many 

 times longer than the flowers ; rachis tomentose. 



HAB. Borders of ditches. July — Aug. 0. Culm 4 ft. 

 high, sub-compress.; pan, 6 — 8 in. long; invol. 

 1 — 2 in. long. 



97. D1GITARIA. Crab-grass. 



1. D. sanguinalis : spikes numerous, fasciculate, a little 

 spreading ; leaves and sheaths somewhat hairy : 

 spikelets oblong ; florets pubescent on the margin. 

 HAB. Cultivated grounds and waste places. Aug. U . 

 Culm decumb. and assurg. ; spik. 4 — 6 ; rach. flex. ; 

 spikelets by pairs. 

 I. 1). glabra: spikes digitate, sub-alternate, (3 — 4,) 

 spreading ; leaves and sheaths smooth ; spikelets 

 ovate, crowded ; calyx equal to the abortive floret, 

 both hairy. 

 HAB. Sandy fields. Aug. — Sept. 0. Culm mostly 

 decumbent ; spik. much spreading, 2 in. long. 

 .';. D. serotina : decumbent; leaves and sheaths verv 



