CHAPTER X. 

 MIGRATION OF WEEDS 



The study of the abundance of weeds and their dis- 

 tribution is one of great importance to the cultivator of 

 the soil. Many of our common weeds occur from the 

 Atlantic to the Pacific. Many of them are of European 

 origin. Some weeds are native to the soil ; others are 

 tropical in origin. It will be found from the list of weeds 

 appended that many of them are common from the Gulf 

 of Mexico to British America. It is also true that Texas 

 has some of its own weeds; that the eastern Gulf states 

 have some peculiar weeds; that the states west of the 

 Missouri River to the Rocky Mountains also have their 

 own characteristic weeds and some localized weeds are 

 found upon the Pacific coast. 



It may be interesting to observe in this connection 

 that some weeds require a considerable length of time 

 before they are permanently established and become a 

 part of our flora. In other instances certain weeds are 

 crowded out. During recent years the writer has found 

 very little evidence of the black mustard in this state, 

 miost of it being replaced by the charlock, or wild 

 mustard of our oat fields. In Utah the awned brome 

 grass has crowded out the quaking brome grass. In 1898, 

 when the writer visited the region of Salt Lake and Og- 

 den he found quaking brome grass the predominating 

 grass on the hillsides, but now the hillsides are covered 

 with the awned brome grass and very little of the quak- 

 ing brome grass could be seen. 



Our eastern weeds are in a large part native to Europe, 

 but there are a number native to Iowa, while others 

 have come from the South and West. The question of 



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