CHAPTER XI 



ROOTS OF PLANTS 



65. Structure of roots. We have already seen the general 

 appearance of roots, in the seedlings of the plants we used 

 for our earlier experiments, in the carrots, beets, and turnips 



used at home, in the roots 

 of trees that have been pulled 

 up to clear the ground, etc. 

 The root hair is a single 

 cell formed by the outward 

 prolongation of one of the 

 skin cells (Fig. 9). The root 

 hairs are the actual absorbing 

 organs. Each root hair lives 



but a short time, and then 

 shrivels up. As the tip of 

 the root grows on, new root 

 hairs are formed. The older 

 skin cells of the root die, 

 and their contents dry out. 

 Together with the shriveled 

 root hairs, these skin cells 

 form a protective covering 

 through which water does 



Fig. 9. The tip of a young root 

 rc^ root cap ; //, /;, root hairs 



not pass very readily. As 

 the plant becomes older and uses up more water, the absorbing 

 area of the root is increased by the formation of many side 

 roots and by the branching of the roots. But it is always in 

 the region near the growing tip of the main root and of the 

 many branch rootlets that absorption takes place. 



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