WORK OF LEA VES: ASSIMILA TION 1 1 3 



The amount of carbon dioxide in the air, if not replenished, at 

 this rate would last the sunflowers about twenty months. This 

 estimate is perhaps excessive. Another estimate is that a hectare 

 (2^ acres) of forest would consume 11,000 kg. (=24,200 Ibs.) 

 carbon dioxide per year. This large amount of carbon dioxide is 

 being continually restored to the air by the burning of wood, 

 coal, etc., and by the respiration of animals so that the normal 

 balance is maintained. The celebrated Krupp works for the 

 manufacture of ordnance at Essen, Germany, alone produces 

 about 2,500,000 kg. (=5,500,000 Ibs.) carbon dioxide per day. 

 It is estimated that the human beings of the earth give back to 

 the air about 1,200,000,000 kg. (2,640,000,000 Ibs. = 1,320,000 

 tons) carbon dioxide each day.* 



III. ASSIMILATION. 



180. Assimilation in plants and animals. The term 

 assimilation usually has a wider application by students of plants 

 than by students of animals. Assimilation in animals is the 

 building up of new living matter and structures of the body, 

 while in plants it has been customary to use the word assimilation 

 not only for the building up of new living substance and new 

 structures of the organism, but also for the formation of food 

 products which are later used by the plant and are also used as 

 food by animals. There is a tendency in recent years on the 

 part of some botanists to distinguish the kinds of assimilation. 

 Those kinds of assimilation which relate to the making of the 

 new life substance, or the making of structures which are part 

 of the living organism, are looked upon as true assimilation. 



Those processes which result in making food products are called synthetic 

 assimilation. The making of sugar and starch (carbohydrates) is called 

 photo synthetic assimilation, because the sun supplies the energy for the 

 initial stages in the process. The making of carbohydrates by the nitrite 

 and nitrate bacteria is called chemo synthetic assimilation, because the chem- 

 ical process or metabolism in changing ammonia compounds to nitrites and 



*See "Text Book of Botany," Strasburger, Noll, etc., 196, English 

 edition. 

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