THE ROOTS 33 



Replace the plant in the soil as it was before. It 

 will be seen to wilt, no matter how much water is 

 poured over it. From this it is fair to conclude 

 that a root from which the hairs have been broken 

 cannot absorb enough water to meet the needs of 

 all the leaves and stems. 



The root-hairs serve the general purpose of in- 

 creasing the amount of absorbing surface of the 

 root, and as a general rule they are most plentiful 

 on the roots of species growing in dry soils, and 

 are almost wholly absent from species growing in 

 wet soils, swamps, or in the water. 



36. Can water he taken in through the leaves ? — 

 Plants which are slightly wilted often revive when 

 the leaves are sprinkled. The wetting of the leaves 

 might be of benefit to the plant in two ways : it 

 might prevent them from drying out by losing the 

 small supply of water they are receiving from the 

 roots, or it might allow them to absorb water like 

 the roots. It is popularly supposed that leaves may 

 take up water, and the following test will throw 

 some light on the matter. Place a young potted 

 specimen of geranium or tomato where it may not 

 receive water until it has wilted from thirst. In- 



