KINDS OF WEEDS AS TO DURATION 



II 



may likewise produce a few nodal roots, but these are 

 generally small and fibrous. The large ragweed (Am- 

 brosia trifida) has a straight tap root with numerous small 

 fibrous roots that descend obliquely into the lower strata 

 of the soil. The horseweed of the same family has a 

 straight tap root, numerous small fibrous roots, and one 

 or more prominent lateral roots. These are at first hori- 

 zontal, descending obliquely later. 



The Spanish needle 

 (Bidens frondosa) and 

 its ally, stick-seed (B. 

 discoidea), are fre- 

 quently found in moist 

 places. Although they 

 belong to the same 

 family as the sunflower 

 and ragweed, they do 

 not ordinarily produce 

 tap roots, but large lat- 



K . & , Fig. 4. Root of common milkweed, 



era! roots instead, single root 14 feet long, with numerous 



which SOOn descend lateral roots. The points indicate 



11- i 4 j.1,- where new roots and stems are form- 



obliquely into the ing Root method of spreading the 

 ground. The Canadian weed. (C. M. King.) 

 goldenrod (Solidago 



canadensis ) , with a horizontal rootstock, produces 

 small lateral roots which soon begin to descend. 

 The ox-eye (Heliopsis scabra), related to the golden- 

 rod, also produces a rootstock from which grow fibrous 

 roots, horizontal at first and then gradually de- 

 scending. In the common mayweed of the same family 

 the straight tap root produces numerous fibrous roots 

 which descend obliquely. The buckhorn and plantain 

 produce a large number of whitish, fibrous roots which 

 are at first horizontal and then descend gradually into the 

 soil. In some plants, as in cowbane, the roots are fas- 

 cicled. In the wild parsnip and the garden parsnip the 



