WEEDS AND POISONOUS PLANTS 



331 



Fig. I 

 burdock. 

 Weed. 



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

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

 are the mulleins, the blueweed, 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 ironweed, 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- 

 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 



Fig. 185. — The Canada thistle. 

 After Weed. 



