The Problems of Plant Distribution 275 



The majority of the Calif ornian plants, however, 

 the flora of the drier mountains and valleys, is of 

 Mexican affinity, and the many showy flowers like 

 the poppies, cream cups, lupins, nemophila, Gilia, 

 Orthocarpus, and Mariposa-lilies, and many others 

 which make so splendid a showing in the open val- 

 leys and upon the hillsides of California in the 

 spring, are for the most part very different from 

 any Eastern flowers and belong to the flora of the 

 great Mexican plateau, of which Arizona and 

 Southern California are really a part. In Central 

 California the two floral regions meet, the north- 

 ern types of the Coast Range often following 

 the stream-beds down into the valleys, and be- 

 tween the hills, where the southern flora predomi- 

 nates. 



As in other settled countries, the character of the 

 flora has been modified by man to a great extent. 

 California, however, being largely an open country, 

 has not had its flora so much altered as was the 

 case in the forested Eastern States. It is true that 

 the forests have been to some extent cut, but more 

 for timber than for clearing the land, the cultivated 

 areas being mainly open country. Cultivation, how- 

 ever, has resulted in the introduction of very many 

 foreign plants, and by irrigation the desert has been 

 transformed into rich fields of alfalfa, or into 

 orange groves and vineyards. With the vines and 

 olives of the early settlers, came in also many weeds, 

 bur-clover, wild-oats, and mustard, which found 



