WEEDS 



469 



being especially abundant in slightly acid soils. Many other 

 kinds of plants, from nettles to goldenrods, are joined in 

 colonies by long underground stems. 1 The sorrel roots and 

 the goldenrod rootstocks produce many buds, and each bud 

 may grow into a new plant. If the rootstock is cut to pieces 

 with a hoe, the process of reproduction is only urged on a 

 little. Every tuber of some sunflowers (Fig. 67), 

 the nut grass, and many other tuber-bearing 

 plants may grow into a new individual. Purs- 

 lane plants when hoed up and left on damp 

 soil at once begin to grow, each bit forming a 

 successful cutting. These are only a few of 

 the hundreds of examples that might be given 

 of vegetative reproduction 

 among weeds. 



The way in which fox- 

 tail grass maintains itself 

 in grainfields, making slow 

 growth while it is over- 

 topped by the wheat, oats, 

 or rye, and then pushes 

 up rapidly, flowering and 

 seeding among the stubble, 

 is an excellent illustration 

 of the importance to the 

 plant of the power to tol- 

 erate shade during the early period of growth. It must be 

 remembered that any qualification that helps the weed in its 

 struggle for existence is a good thing for the weed, even if it 

 is discouraging from the point of view of the farmer. 



The survival of mullein and ironweed in pastures, and of 

 dog fennel, smartweeds, and the offensive-smelling, poisonous 

 Jimson weeds (Fig. 300) in barnyards, are only a few examples 

 of the many that could be given to show how some weeds 

 persist by being uneatable or positively offensive. 

 1 See Bulletin 76, Kansas Agr. Exp. Sta. 



FIG. 353. Portion of a plant of the com- 

 mon sorrel 



The leaf is drawn about one half natural 



size. The running roots of a large specimen 



would be at least sixty times as long as the 



piece here shown 



