14 THE STRUGGLE FOR EXISTENCE 



time. At first sight one might think that the better the conditions of 

 existence the less active is the struggle for life, and the greater the 

 number of trunks that can survive with age on a unit of surface. Let 

 us, however, look at the data of the foresters. For an example we 

 will give in Table I the number of the fir trunks in the government of 

 Leningrad (Northern Russia) corresponding to five different types 

 of life conditions (Type I represents the best soil and ground condi- 

 tions; V, the worst ones). 



These data show, contrary to our expectations, that the better are 

 the soil and ground conditions, the more active is the struggle for life, 

 or in other words the smaller the number of trunks remaining on a 

 unit of surface and, consequently, the greater the percentage of those 

 which perish. If we think out this phenomenon, it becomes quite 

 understandable : the more favorable the environment is for the plants' 

 existence, the more luxuriant will be the development of each plant, 

 the sooner will the tops of the trees begin to close above, and the 

 earlier the oppressed individuals become isolated. Also, in better 

 conditions of existence, every individual in the adult state will be 

 more developed and occupy a greater space, but the individuals will 

 be fewer in number. Investigations show that this is a general rule 

 for all the forest species (Sukatschev, '28, p. 12). 



Similar data were obtained by Sukatschev ('28) in experiments 

 with the chamomile, Matricaria inodora, on fertilized and non-ferti- 

 lized soil. In counting up the individuals remaining at the end of 

 summer (August 17), the following decrease of the original number of 

 individuals was ascertained (see Table II and Fig. 1). 



Here likewise in better conditions of existence competition pro- 

 ceeds with greater intensity, and the per cent of individuals which 

 perish is greater. 



The results obtained by botanists are certainly characteristic for 

 the ontogenetic development of plants, but at the same time they 

 give us an approach to the quantitative appreciation of the intensity 

 of the struggle for existence, the whole significance of which was 

 already clearly understood by Darwin. In the next chapter we shall 

 consider the struggle for life in animals, and there, using entirely 

 different methods, we shall endeavor to formulate quantitatively the 

 intensity of this struggle. 



(3) In field observations the question often arises as to the struggle 

 for existence in mixed populations, about which Darwin wrote: "As 



