ABSORPTION OF WATER 



131 



becomes evident upon comparing the above figures with the 

 amount of water entering into chemical reaction during the same 

 period in the synthesis of carbohydrates. Under the environment 

 of central Europe, for every kilogram of water absorbed only 3 to 

 4 g. of dry matter are formed. If it be assumed that the dry sub- 

 stance consists of carbohydrates and that half of this weight is 

 made up by carbon, the other half consisting of the elements of 



ii-K-.v.'W ':,'.'. - '... ": 



Fig. 49.— Amount of water evaporated during the summer by one maize plant 



(after Sinnolt). 



water, then it will be found that of the 1,000 parts of water that 

 pass through the plant, only 1.5 to 2 parts are utilized in the process 

 of nutrition. The remaining 998, or even 998.5 parts pass through 

 the plant in order to compensate for evaporation and to maintain 

 a sufficient degree of saturation in the tissues of the plant. 



Such lavish expenditure naturally requires a no less rapid 

 absorption of water. This task is performed chiefly by the roots. 

 The real dimensions of the root system are much greater than most 



