ABSORPTION BY ROOTS 



167 



largely magnified in Figure 38. These root-hairs, 

 which cluster about the 

 growing point of the 

 young roots, are the 

 organs of the plant 

 that absorb soil-water. 

 They are of value only 

 for limited periods of 

 time, for as they grow 

 older, they lose their 

 power of water absorp- 

 tion. In fact, they are 

 active onl}^ when they 

 are in actual process 

 of growth. It follows, 

 therefore, that water 

 absorption occurs near 

 the tips of the growing 

 roots, and whenever a 

 plant ceases to grow 

 the water absorption 

 ceases also. The root- 

 hairs are filled with a 

 dilute solution of vari- 

 ous substances, as yet 

 poorly understood, „ , . 



, . , , . Fig. .38. // Wheat root, showing 



which plays an miJJOr- boU particles dinging to the lower part 

 tant part in the ab- ''^'=''' *^^ root-hairs are active. 



sorption of water and plant-food from the soil. 



