GEOLOGICAL AND GEOGRAPHICAL DISTRIBUTION 241 



complete exclusion of the native plants. Originally the 

 whole of Atlantic North America was an unbroken for- 

 est, with an undergrowth of delicate shade-loving plants. 

 With the clearing away of the primeval forest these 

 plants quickly perished, and a host of foreign weeds, 

 grasses, thistles, dandelions, docks, plantains, rushed 

 in to occupy the waste room. As civilization pushed 

 westward, the hordes of these European immigrants 

 were met by the prairie plants, which were able to cope 

 with them successfully, so that now the farmer has to 

 contend with two sets of enemies, the European weeds 

 on the one hand, and the prairie weeds, rag-weed, bur- 

 marigold, Rudbeckia, sunflowers, etc., on the other, 

 These weeds are transported with grain in railway 

 cars, or cling to the coats of animals or the clothes of 

 human beings, and in these days of rapid transit, plants* 

 have also taken advantage of the improved means of 

 travel. 



In most parts of California, owing to the long dry 

 season, most of the weeds from northern Europe do not 

 thrive, and instead we find weeds whose home is upon 

 the shores of the Mediterranean. Probably introduced 

 by the original Spanish settlers, wild oats, alfilaria, 

 bur-clover, and other south European plants have es- 

 tablished themselves in the sunny valleys of California, 

 where they grow side by side with the poppies and 

 lupines, which, however, are quite able to hold their 

 own. 



