THE (JRAMIXEiE OF NORTH AMERICA. 669 



(•oTiliiied to the Western coast, wliile the otiier 4 are all east of the 

 mountains and, with a single exeeption, east of the Mississippi River. 

 Almost the same may be said of the 'J si)ecies of JJetitltdmjmu. 



" Ely mils, with its 18 species, has representatives in nearly every 

 state excepting Florida, but is most abundant in the Kocky Moun- 

 tain region and on the Pacific slope, California and Oregon having 

 8 si)ecies each, while New England has but 3 and Texas 5. 



** J'Jrttf/rns/is is another genus of wide distribution, 5 of its 25 

 species being found from the Atlantic to the Pacific, while but 3 

 species, 1 in California and 2 in Florida, are confined to single 

 states. 



" Fvstnra is also widely dispersed, and is so extremely variable 

 that it is very difficult to define the limits of many of the so-called 

 species or their geographical range. 



" Glyceria and Afropis form a group with representatives in 

 nearly every state, though more abundant northeast than elsewhere; 

 New England having the greatest number, 12, while Minnesota has 

 6, (^)regon 7, I'exas 2, and Florida only 1. 



'' Melica with its 18 species is strongly Avestem, having 12 spe- 

 cies in California and 11 in Oregon, while only 2 arc found east of 

 Colorado and Texas. 



" Mi(hlenher(iia centres in the arid regions of the Southwest. 28, 

 or more than half of its 46 species, being found in Texas, while Ari- 

 zona has no less than 30, or about two-thirds of the entire number. 



" Oryzoptiis in some form is found in nearly the Avhole country 

 excepting south of the Ohio Kiver, where its occurrence is noted but 

 once. 



'* J^anicnm, with some of its 83 species, covers the entire country, 

 but its distribution is very unequal and appears to be influenced by 

 both climate and the cultivation of the soil. Many of its forms are 

 rarely seen excepting in cultivated fields, where they may grow * as 

 thick as crab-grass,' and many others have a limited range. Many 

 species which are annuals in the North become perennials in a 

 miltler climate, and so we find both species and individuals becoming 

 more numerous as we go South. New England has 21 species, 

 while Florida has 45; Minnesota has 14, and Oregon oidy 5, while 



