196 PLANT PHYSIOLOGY 



in their Bulletins, Nos. 28, 36, and 40, and by Schreiner and 

 Reed in the Bulletin of the Torrey Botanical Club, 34, 1907, 

 279. A note by Fletcher in Nature, 76, 1907, 518, and another 

 in the same journal, 69, 1903, 162, should also be consulted. 



SECTION 2. THE PROCESSES OF INCREASE. 



We have now considered the making of its food by the plant 

 and the use thereof, with the modes of absorption, transport, 

 and removal of the various substances involved. All of these 

 processes, however, are concerned simply with the maintenance 

 of the life of the individual, and are without particular refer- 

 ence either to the increase of those individuals or their adjust- 

 ments to their surroundings. We come now to consider the 

 processes of increase, and it is evident that they fall into two, 

 according as they are concerned with: 



1. The increase of individuals in size, or Growth. 



2. The increase of individuals in number, or Reproduction. 



9. GROWTH. 



Observation of the growth of individuals soon shows that 

 this process includes two phases quite different in nature, which 

 are: 



(a) Enlargement in bulk of parts already formed, or Auxesis. 



(b) Formation of new parts, or Differentiation. 



(a) Auxesis. 



Turning to enlargement, or auxesis, and seeking a basis for 

 its exact study, it becomes evident that, as the higher plant is 

 built up by the repetition of a large number of a few kinds of 

 organs, notably leaf, root, and stem, we must study the enlarge- 

 ment of each of these. The first step in this inquiry will natu- 

 rally have reference to whether each of these organs swells 

 uniformly throughout, or more rapidly in some parts than others 

 thus presenting to the student the definite inquiry: 



Do growing leaves, roots, and stems enlarge uniformly through- 



