Prevalence of Weeds. 9 



I. The number of zveed species. The 

 number of the various species of weeds 

 which infest the different portions of the 

 United States and of the provinces of Can- 

 ada has not yet been accurately determined. 

 The story of their distribution has not yet 

 been fully told, and their number is con- 

 stantly increasing. It would serve no good 

 purpose to enumerate the various species, 

 or even to try to give an approximation of 

 their number. Weeds are probably quite 

 as numerous and varied now in America as 

 in Europe, where it is well known that they 

 have been constantly increasing in number 

 and variety w'ith every passing century. In 

 addition to the noxious weeds of America 

 that are native to the continent, the greater 

 portion of those that have long harassed 

 the inhabitants of Europe are now giving 

 trouble to the inhabitants of America. 



Our most troublesome and aggressive 

 weeds are foreigners. The Canada thistle, 

 which seems so completely at home in the 

 central provinces of the Dominion and the 

 northern portion of the United States, was 

 imported from Europe. The same is true 

 of some varieties of the sow thistle. The 

 wild oat, the ox-eve daisv, the burdock, the 



