WEEDS AND POISONOUS PLANTS 



331 



F IG. 184. The 

 After 



black-eyed Susan. The wild carrot and the wild parsnip, 

 both members of the parsley family, are biennials ; and so 

 are the mulleins, the blue weed, the hound's 

 tongue, and the wild teasel. 



351. Perennial Weeds. The weeds of 

 this group multiply by means of seeds, but 

 the fact that parts of them live from year 

 to year makes it possible for them to in- 

 crease their numbers in other ways as well. 

 Many of them, such as the Canada thistle 

 and the horse-radish, spread very readily 

 by means of the growth and branching of 

 their underground parts. 

 Indeed, the horse-radish in 

 the United States depends 

 almost entirely upon this 

 vegetative method of propa- 

 gation and forms seeds but 

 rarely. The composite family, to which so 

 many annual and biennial weeds belong, 

 contributes also a goodly 

 number of perennial weeds ; 

 the list includes the Canada 

 thistle, the field sow thistle, 

 the iron weed, the dandelion, 

 and the marguerite or ox- 

 eye daisy. Among the 

 grasses that cause trouble 

 as weeds are the well- 

 known quack grass, the 



Johnson grass, and Ber- 

 FIG. 185. The Canada thistle. J 



After Weed. muda grass. Other peren- 



nial weeds are the bind- 

 weeds, horse nettle, milkweeds, plantains, field garlic, Indian 

 hemp, field sorrel, and yellow dock. The brake is one of 



