90. Cross-section of a root, as it grows in the soil, showing the relations of the 

 'root-hairs (rh) to the soil-particles (sp) and the air-spaces (a): this soil is 

 represented as containing the maximum amount of water compatible with 

 good plant-giowth. Whenever a root-hair absorbs water, more flows toward 

 it from the surrounding region; a single root -hair is thus enabled to 

 drain a considerable area. The water absorbed by the root-hairs passes 

 through the loose outer rind or cortex of the root to the wood-cells (shown 

 as four groups of thick-walled cells in the center of the root); alternating 

 with the four groups of wood-cells, are four groups of thin-walled bast, while 

 in the center is pith. 



