146 



Physics of the Soil. 



into the stem and leaves the water absorbed ; and third, to 

 act as an anchor or support, holding the plant upright in 

 the soil, air and sunshine. 



FIG. 44. A, Root-hairs of mustard plants, with soil adhering, and with 

 soil removed. B, root-hairs of wheat, when very young, and four 

 weeks later. (After Sachs.) 



178. The Absorbing Portion of Roots. It is the general 

 belief of plant physiologists that the active portion of roots 

 that which is immediately concerned in gathering the 

 water from the soil is what are known as root hairs, rep- 

 resented at the left of A, Fig. 44, and at A buried in the 

 soil grains in the same figure. In Fig. 46 is a much en- 

 larged view of a single root hair which has worked its way 

 in among the soil grains where it is in place to absorb soil 

 moisture and soluble salts. The appearance of root hairs 

 in relation to soil grains can be clearly demonstrated by 

 growing plants in rather coarse sand between glass plates 

 as represented in the apparatus shown in Fig. 45. 



