PLANT PHYSIOLOGY 117 



is a poison, formaldehyde, and must be recombined immediately 

 upon its formation, presumably changing into a simple sugar 

 by addition and rearrangement of its molecules thus 6CH2O = 

 CeH^Oe or glucose from which starch is formed by the loss of 

 water, thus CeH^Oe H^O = CeHioOs or starch. This starch 

 is stored temporarily in the leaves, or it is gathered up as 

 glucose which is soluble, by the collecting tubes and carried 

 through the vascular bundles to the rhizome where, in the 

 parenchyma cells, it is permanently stored as starch to be used 

 as needed by the plant. At night, in this way the starch is re- 

 moved from the leaves but with the advent of daylight the manu- 

 facturing process begins again. This process of starch manu- 

 facture by photosynthesis is the essential difference between 

 animals and plants, and the plant has this power by virtue of 

 chlorophyll. 



From this point on in nutrition, animals and plants alike have 

 the power to manufacture proteids. In the plant the process 

 can be followed more easily than in animals, some of the simpler 

 compounds like asparagin consisting of nitrogen added to the 

 carbohydrate (CJHg^Os), and from this relatively simple 

 amide proteid may be formed by the addition of the essential 

 elements. The formation of these substances is obscure, the 

 action presumably, being brought about through the agency of 

 synthesizing enzymes. In animals the proteid materials 

 taken as food provide the necessary elements for this synthesis 

 but in plants the proteids must be built up step by step. Plants 

 thus are essentially constructive while animals are destructive. 



In the manufacture of starch more oxygen is liberated from 

 combination than can be used and this diffuses through the 

 leaves and into the air while carbon dioxide is taken in. Plants 

 and animals therefore would seem to be well adapted for mutual 

 existence side by side. But the plant does more or less work and 

 utilizes its substance in providing the energy necessary for this 

 work, while waste matters in the form of CO2 and water and 

 probably a nitrogenous waste, are formed. As in animals the 

 C02 is given off into the air while oxygen is taken into the 

 plant from the air, but this fundamental process of respira- 



