GRAMINE.E. 399 



1. P. ciliatifolium Mich. : culm decumbent ; leaves hairy and ciliate ; 

 sheaths hairy ; spikes 1 2, rather lax, indistinctly 3-rowed. P. cili- 

 atum Pursh. 



HAB. Sandy fields. N. Y. to Car. Sept. 1. Culm 18 inches 

 long, slender and simple. Spike mostly solitary, terminal. 



2. P. setaceum Mich. : culm erect ; leaves and sheaths villous ; spike 

 mostly solitary ; flowers in 2 rows. P. pubesccns Muhl. 



HAB. Sandy fields. N. Y. to Car. July. . CWro 12 feet 

 high. Spike on a long terminal peduncle. 



3. P. lane, Mich. : erect, very smooth ; leaves short, very smooth ; 

 spikes numerous, (3 6,) alternate; flowers 2-rowed, smooth. 



HAB. Dry meadows. Penn. to Car. Aug. If. Culm 1 2 

 feet high. Spikes spreading. 



4. P. stoloniferum Bosc : spikes in elongated racemes, somewhat 

 verticillate, spreading ; flowers serrulate-ciliate, transversely rugose ; 

 leaves short, subcordate ; culm prostrate at base. 



HAB. Cedar swamps. N. J. Aug. 1. Culm 2 feet long, 

 branched, geniculate, stoloniferous. Spikes very numerous, 

 (3050.) 



18. CENCHRUS. Linn. 



Involucre 1 3-flowered, many-parted, bristly without, 

 finally hardened. Glume 2-flowered, 2-valved ; outer valve 

 smallest. Florets dissimilar; the outer sterile, the other 

 perfect. Scales none. Triandria. Monogynia. 



1. C. echinatus Linn. : spikelets approximated ; involucres 10-part- 

 ed, villous. 



HAB. Sandy soils. N. J. to Geor. Aug. <j$. Culm erect or 

 procumbent, 1 2 feet long. Spikes consisting of 6 10 heads. 



2. C. tribuloides Linn. : spike with alternate spikelets ; involucres 

 entire, spiny. 



HAB. Sandy soils. N. J. to Flor. July, Aug. $j$.Culm 18 

 inches high. Dr. Torrey thinks it a variety of the preceding. 



19. TRIPSACUM. Linn. 



Monoecious. STERILE FL. Glume 2-flowered ; outer one 

 sterile; inner neuter. Corol a membranous glume. FER- 

 TILE FL. Glume 1-flowered, surrounded by a 1-leaved invo- 

 lucre, perforated near the base. Corol a 2-valved glume. 

 Styles 2. Seed 1. Monoecia. Triandria. 



T. dactyloides Linn. : spikes 3, clustered ; sterile florets near the top, 

 fertile at the base. 



1. monostachyon Torr. : spike solitary. T. monostachyon Wittd. 

 HAB. Meadows. N. Y. to Car. W. to 111. Aug. ll. 

 57 feet high. Spikes large. 



