STRUGGLE IN NATURAL CONDITIONS 



15 



the species of the same genus usually have, though by no means in- 

 variably, much similarity in habits and constitution, and always in 

 structure, the struggle will generally be more severe between them, 

 if they come into competition with each other, than between the 

 species of distinct genera." Lately, botanists have tried to approach 

 this problem experimentally. It became evident that, actually, in a 

 number of cases competition is keenest when the individuals are most 



Percentage, of perished individuals 



15.1% 



5.8% 



good Bad 



conditions 



Fig. 1. Intensity of the struggle for existence in the chamomile, Matricaria 

 inodora, on fertilized and non-fertilized soil (dense culture). 



TABLE II 



Decrease of the number of individuals in the chamomile {Matricaria inodora) 



expressed in percentage of the initial number 



From Sukatschev ('28) 



similar. The more unlike plants are, the greater difference in their 

 needs, and hence some adjust themselves to the reactions of others 

 with little or no disadvantage. This similarity must rest upon vege- 

 tation or habitat form, and not merely upon systematic position 

 (Clements, '29). Researches on competition in mixed populations 

 consisting of different kinds of cultivated plants were undertaken by 

 many investigators (e.g., Montgomery, '12). Particularly interesting 



