72 Principles of Plant Culture. 



absorb water, with the food materials it contains. The 

 root-hairs greatly increase the absorbing surface of the 

 roots, just as leaves increase the absorbing 

 "^ VN surface of the plant above ground. Each 

 root-hair consists of a single elongated 

 cell (Fig. 30), and is filled with proto- 

 plasm, as are the cells in other living 

 I jjjjjjl parts of the plant (13). As the extrem- 

 ity of the root advances through the soil 

 by growth, new root-hairs are formed in 

 front of the older ones, while those far- 

 thest back as rapidly die off, so that only 

 a short portion of a rootlet bears root- 

 hairs at any one time. In Fig. 27 root- 

 hairs are visible in the left glass, and in 



FIG. 29. Seed- 

 lings of turnip Fig. 6 they may be seen on the hpyocotyl 



showing root- 



hairs. (After of some of the germinating corn grains. 



.Frank and 



Tschirch.) i n Fig. 29 A and in Fig.* 28 the parts of 

 the root bearing root-hairs are indicated by the sand 

 which adheres to these parts. It is usually difficult to 

 see the root-hairs of plants growing in the natural soil, 



PIG. 30. Magnified root-hair of wheat, in contact with soil 

 particles. (After Sachs.) 



but they may sometimes be discovered with the help of 

 a pocket magnifying glass by carefully removing the 

 soil particles about the younger roots, when the silky 

 network of root-hairs may be seen filling the smaller 



