TRANSMUTATION. 355 



the construction of new parts. The changes by which these 

 processes are performed take place in the protoplasm which 

 receives and in some way disposes of the newly formed food. 



926. Supply of energy for work. This is furnished by the 

 process of oxidation. It will be remembered that the inorganic 

 materials concerned in the production of the food of the plant, 

 namely, carbonic acid and water, are highly oxidized compounds. 

 By assimilation a part of the oxygen is liberated, and the or- 

 ganic matter formed is some carbohydrate capable of oxidation. 

 The reception of oxygen, the oxidation of the oxidizable matter, 

 and the release of the products of oxidation by the plant are 

 collectively termed respiration. 



927. Repair of waste. The living matter of plants, like the 

 living matter of animals, being the seat of all the activities 

 manifested by the organism, is constantly undergoing waste 

 and demanding repair. The repair of waste is proper nutri- 

 tion. 



928. The construction of new parts. It has been shown (Chap- 

 ter X.) that by the appropriation of nitrogen by the plant proteids 

 are formed, and these are in great part utilized in the produc- 

 tion of new protoplasmic matter. So far as the latter is an 

 actual increase in substance, and not a mere repair of waste, 

 it represents true growth. The growth of any root, stem, or 

 leaf consists in the formation of new cells and the increase 

 of these in size. In this process the production of new cell- 

 wall is of course the most conspicuous phenomenon. The per- 

 manent increase in size of the cell- walls of a plant disposes of a 

 large part of the organic matter which is prepared by assimila- 

 tion, and this phase of growth is apt to divert attention from 

 that which really underlies it ; namely, growth of the protoplasm 

 itself. 



929. For convenience, the various chemical changes which 

 go on within the plant may be divided into two groups ; namely, 

 transmutation and complete oxidation. In the former, the or- 

 ganic matter changes its properties in some way, either by 

 the addition of new materials or by the reconstruction of its 

 existing molecules, but, notwithstanding the change, still re- 

 mains organic matter ; while in the latter it is resolved into its 

 original inorganic components. The change of one kind of food 

 into another, the transformation of starch into cellulose, and the 

 formation of proteids, are good examples of transmutation : the 

 consumption of food for the release of energy, an example of 

 complete oxidation. The first of these groups of changes cor- 



