Prci'alcnce of Weeds. ii 



attempt is made to exterminate them, it is 

 to prove successful. Happily the number 

 of varieties of weeds which are really seri- 

 ously harmful to crops and difficult to erad- 

 icate is not very large. In the present state 

 of our knowledge of the subject, it would 

 not be safe to name a definite number which 

 w^ould cover the entire list, nor would it be 

 judicious to do so, as new varieties are com- 

 ing forward all the time. Notwithstand- 

 ing, it would probably be not incorrect to 

 say that at the present time the varieties of 

 really noxious weeds in the United States 

 and Canada do not number more than thirty 

 or forty, and it is greatly encouraging to 

 reflect that we seldom find more than half 

 a dozen kinds entrenched in any one local- 

 ity. 



2. The extent to zvhich zvceds have been 

 allozved to multiply. The extent to which 

 certain varieties of noxious weeds have 

 been allowed to multiply is simply alarm- 

 ing. Some of them are, in a sense, taking 

 possession of the land. Notably is this true 

 of wild mustard, the Canada thistle, and 

 wild oats in the Red River Valley and simi- 

 lar grain-growing sections, of quack grass 

 in some localities, and of wild barlev and 



