40 



DEPARMENT OF AGRICULTURE GEORGIA. 



[326] 



erting a pressure on every part of the interior of the plant. 

 It varies in different plants, and in the same plant under 

 different circumstances. 



Fig. 4. 



It is greatest when the roots are in a state of most rapid 

 development, and under favorable circumstances as to sup- 

 ply of warmth and moisture, but manifested most plainly 

 just before growth commences in spring, as seen in the 

 sugar maple, grape vine, etc. 



There are three forces which take part in the action of 

 the roots of plants in the performance of their functions of 

 absorption of crude plant-food, and the simultaneous as- 

 similation of the same in adding to their absorbing surface. 

 These are osmose, acting through the cellular system ; ad- 



