WEEDS 77 



some because it thrives late in the season after the usual 

 cultivation of the crops has ceased. Two important 

 weeds in blue-grass lawns are crab-grass and annual blue- 

 grass. The latter thrives in the spring, making an appear- 

 ance pleasing to the eye, but later dies, leaving unsightly 

 bare spots. In the same way crab-grass, later in the 

 season, leaves brown patches as the plants die. 



105. On the Pacific coast other species of grasses 

 become weeds. A very noticeable group are the annual 

 species of Bromus. They are of some value as forage 

 when young but soon become too dry and prickly from the 

 awns of the inflorescence to be palatable. The principal 

 species are Bromus commutatus, B. hordeaceus, B. ruhens, 

 B. tectorum and B. villosus (Par. 260). Another species, 

 B. secalinus, the common cheat or chess, is found in grain 

 fields throughout the northern United States. The wild 

 oat is abundant on the Pacific coast in grain fields and on 

 fallow lands, but possesses a mitigating character in that 

 it can be used for hay (Par. 239). Several weedy species 

 belong to the genus Hordeum, the inflorescence of which 

 possesses numerous rough aAvns that are troublesome 

 when mixed with hay. There are three annual species, 

 H. pusillum, H. Gussoneanutn and H. murinum. The last 

 is a common weed in alfalfa fields where it is called fox- 

 tail and barley-grass. 



106. Perennial weedy grasses. — Of the group that 

 lack creeping rhizomes there are few that are troublesome. 

 One of the worst of them is Hordeum juhatum, which in 

 the West often infests alfalfa fields. It is called squirrel- 

 tail-grass, but locally is known as foxtail in Wyoming, 

 barley-grass in Utah, and tickle-grass in Nevada. 



Many species become conspicuous in overgrazed pas- 

 tures or ranges because not eaten readily by stock. To 



