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rious margined, concave or ventricose ; flowering glumes imbricated, 

 appressed or spreading, broad or roundish, ventricose, often heart- 

 shaped at the base, five to many nerved ; palet much shorter than 

 its glume, hyaline, on the margin two-nerved. 



1. B. media, Linn. Naturalized in some places. Quaking grass. 



2. B. minor, Linn. Naturalized in some places. Quaking grass. 

 These are small grasses often used for ornamental purposes. 



Poa, Linn. 



Spikelets somewhat compressed, usually two to five flowered, in a 

 narrow or loose and spreading panicle, the rhachis between the 

 flowers glabrous or sometimes hairy, the flowers generally perfect, 

 in a few species dioecious ; outer glumes commonly shorter than the 

 flowers, membranaceous, keeled, obtuse or acute, one to three nerved, 

 not awned ; flowering glumes membranaceous, obtuse or acute, five 

 or rarely seven nerved, the intermediate nerves frequently obscure, 

 often scarious at the apex and margins, smooth or pubescent, often 

 with a few loose or webby hairs at the base ; palet about as long as 

 the flowering glumes, prominently two-nerved or two-keeled. 



1. P. abbreviata, R. Br. Oregon to the Arctic coast. 



2. P. alpina., Linn. Mountains of New England and Rocky Moun- 



tains. 

 P. alpina, var. minor. Rocky Mountains. 

 P. alpina, var. purpurascens, Vasey. (Poa purpurascens, Vasey.) 



Oregon and Rocky Mountains. 



3. P. alsodes, Gr. New York, New England, and Alleghany 



Mountains. 

 P. alsodes, var. Wolfii, Vasey. Illinois. 



4. P. andina, Nutt. Rocky Mountain region. 



5. P. annua, Linn. Introduced. 



6. P. arachnifera, Torr. Texas Blue grass. Texas to New 



Mexico. 

 P. arachnifera, var. glabrata, Vasey. Texas Blue grass. Texas 

 to New Mexico. 



This species was first described by Dr. John Torrey in the report 

 of Captain Marcy's exploration of the Red River, of Louisiana, as 

 having been found on the headwaters of the Trinity, and named 

 Poa arachnifera from the profuse webby hairs growing about the 

 flowers, although it is found that this character is very variable, 



