C* 







EOOT-HAIKS 



261 



cell, but having a length which may reach to several 

 millimetres. They are scarcely visible to the naked eye. 

 They stand out straight from the epidermis, and occur 

 in a zone just above the active growing-point not only 

 of the main root, but also of its branches. As the tip 

 of the root advances with growth, new root-hairs are 

 produced, and the older ones behind them wither, so 

 that the effective hairs always occur in a zone very close 

 to the root tip. The older portions of the root, which 

 become woody and invested with cork, do not absorb 



FIG. 77. 



A, Young root, with root-hairs penetrating the soil ( x 7); B, root-hairs, 

 under higher magnification, showing adherent particles of soil. 



water. They grip the soil, and hold the plant fast in 

 its site, and their hold is such that no ordinary strain 

 will dislocate the operations of the root-hairs. These 

 portions, too, by virtue of the vascular system which 

 becomes developed in them, provide means of transport 

 of the water, and its nutritive contents, from the absorp- 

 tive hairs to the portions of the plant where they are 

 needed. 



Water is not permitted to stagnate in the tissues of 

 a plant. If it is to be of use, it must circulate, and 



