72 



CHEMISTRY OF FARM PRACTICE 



while the solution containing the greater amount of material 

 will flow more slowly, being obstructed by the membrane. 

 The inflow of water into the plant is thought to be in re- 

 sponse to the pressure thus generated, the cell wajl of the 

 root hair being the membrane and the sap within the cell 





(a) 



FIG. 24. (a) Root hairs, (6) 

 close contact of root hairs 

 with soil particles. 



FIG. 25. Osmosis shown with 

 a bladder membrane. 



being more concentrated than the soil solution. The dif- 

 fusion of the plant food from cell to cell throughout the 

 plant is considered to be due to the same cause. 



Every element or compound in the soil solution has 

 its specific relationship to osmosis and, in this way, the 

 amount of eah material imbibed is governed. Some 



