IPostelsia 49 



not been discussed fully, but many are 

 mentioned in the accounts of roadside 

 plants and plants of the mesas. The 

 plains are more or less well known to 

 everyone who has lived in the Missis- 

 sippi basin, for the plains are merely 

 exaggerated prairies, larger and drier 

 than the prairies of the north central 

 states, but otherwise very similar. 



Where the plants of the plains meet 

 the mountain forms on the foothills and 

 mesas, there is a mixed flora, rich in 

 species both of western and more 

 eastern genera. Few of the plains 

 plants ascend to any great altitude, and 

 few mountain forms make their way 

 far out on the plains. The Yucca 

 and certain cactuses of the plains may 

 reach an altitude of 2,000 meters, or 

 a little more. Many roadside plants 

 creep up even higher. Very few plains 

 plants pass above 2,300 meters. 



