NUTRITION, STORAGE, AND RESPIRATION 117 



sun ages ago, may be again available in combustion for modern uses. 

 The initial step of Constructive Metabolism appears to be taken 

 quickly in the Green Plant exposed to the Sunlight. Destructive 

 Metabolism may involve many stages of re-oxidation, and they may 

 be spread over long intervals of time. Time is not really a factor in 

 the process, as is shown by the coal we use daily, or by any hermetically 

 sealed food that we consume. 



These general remarks are, however, a digression from the study of 

 the Plant. Returning to the Green Plant itself, its Constructive Meta- 

 bolism provides new material. This is required in the first instance 

 for the nourishment and growth of its several parts : that is for the 

 maintenance of the individual. But secondly, it is required for the 

 increase in number of individuals. The propagation of the race can 

 only be carried out when sufficient material is at hand from which 

 to form the new germs. 



