ABSORPTION OF WATER 49 



46. Importance of Root-hairs. In Chapter II attention 

 was called to the root-hairs. Their chief function is the 

 absorption of water and dissolved substances from the. 

 soil. This may be demonstrated by a very simple 

 experiment. If a young seedling of bean, corn, or any 

 other plant growing in soil, is pulled up, care being taken 

 not to loosen the dirt from the roots, then properly 

 transplanted in another place, and well watered, it 

 will continue to grow, having suffered no apparent injury. 

 If another seedling, of about the same size and vigor is 

 pulled up, and the soil removed from the roots by means 

 of the fingers, some of the very delicate root-hairs will 

 be torn off with the soil, and many others will dry up owing 

 to too prolonged exposure to the air. If this seedling 

 is then transplanted, it will recover with difficulty, or 

 it will wilt and die, even though well watered, showing in 

 a very clear manner the inability of a plant to take in 

 water when deprived of its root-hairs. 



46. Location of Root-hairs. Root-hairs for study may 

 be easily secured by germinating seeds in a moist chamber, 

 formed by inverting a flower pot over a saucer of water. 

 Small seeds, such as flax or white mustard, will readily 

 adhere to the moistened inner surface of the inverted 

 flower pot. Within 24 to 36 hours the roots will have 

 developed to a length of several millimeters, and the 

 root-hairs will appear as a delicate white "fuzz," near 

 the end of the root, but not extending clear to the tip 

 (Fig. 36). On older roots it may be seen that the root- 

 hairs are confined to a relatively short zone, only a 

 few millimeters long. The hairs nearer the root-tip are 

 shorter than those further back, indicating that they are 

 younger. 



4 



