COMPETITION 167 



creases the amount available. The inevitable result is that 

 the successful individual prospers more and more, -while the 

 less successful one loses ground in the same degree. As a 

 consequence, the latter disappears entirely, or it is handi- 

 capped to such an extent that it fails to produce seeds, or 

 these are reduced in number or vitality. 



Competition in vegetation furnishes few instances as 

 simple as the above, but this will serve to make clear the 

 simplest case of ordinary competition, i. e., that in which 

 the individuals belons; to a single species. The various in- 

 dividuals of one species which grow together in a patch 

 shuw relatively slight differences, in height, width, leaf 

 expanse or root surface. Still, some will have the largest 

 surfaces for the impact of water, heat and light, while 

 others will have the smallest: the majority, perhaps, will 

 occupy different places between the extremes. The former 

 will receive more than their share of one or more factors. 

 The reaction thus produced will operate upon the plants 

 subject to it inversely as the amount of surface impinged 

 upon. The usual expression of such competition is seen in 

 the great variation in height, branching, etc., of the 

 different individuals, and in the inability of many to pro- 

 duce flowers. This is particularly true of annuals, and of 

 perennials of the same generation. In the competition be- 

 tween parents and offspring of the same perennial species, 

 the former usually have so much the advantage that the 

 younger plants are often unable to thrive or even germin- 

 ate, and disappear, leaving a free space beneath and about 

 the stronger parents. This illustrates the primary law of 

 competition, viz., that this is closest when the individuals 

 are most similar. Similar individuals make nearly the 

 same demands upon the habitat, and adjust themselves least 

 readily to their mutual reactions. The more unlike plants 

 are, the greater the difference in their needs, and some are 

 able to adjust themselves to the reactions of others with 

 little or no disadvantage. 



In accordance with the above principles, the competition 

 is closer between species of like form than between those 



