4 8 



SOILS 



CROSS-SECTION OF ROOT HAIR 



or four hours. You will note shortly after the apparatus 

 has been so placed that the molasses in its receptacle is 

 gradually rising above the level of the water outside. If 



you use a slender tube, it may 

 overflow even at the top. 



The increase in the contents 

 of the tube or lamp chimney is 

 due to the entrance of water 

 from the outside ; for the 

 water has passed through the 

 thin bladder, or membrane, 

 and has come to occupy space 

 in the tube. While the molas- 

 ses seeks passage through the 



membrane to the water below, it does so very slowly, so 

 slowly it is scarcely noticeable. The in- 

 teresting behavior is this : There are no 

 holes or pores in the membrane, but still 

 there is a free passage of liquids in both 

 directions, although the more heavily laden 

 solution must move more slowly. 



Now, root hairs behave in the manner 

 here described. Soluble nourishment 

 needed plant food passes from the outside 

 to the inside through the delicate membrane 

 of the root hair. Thus does food enter the 

 plant root. From the root hairs, foods are 

 carried into the root. Thus do we say a 

 root takes nourishment by osmosis. 



The sap current. Growing plants are 

 ever busy gathering food, the root hairs 

 securing nourishment from the soil and the 

 leaves carbon from the air. As soon as the carbon is man- 

 ufactured into starch and sugar, these manufactured foods 



ROOT HAIRS 



