ECOLOGICAL SUCCESSION. 85 



clearly suggested when we compare the forest and the shrub 

 covered bluff where forest animals occur. Plants grow from 

 seeds only under a very limited range of conditions. However 

 if trees are given a few years' growth under favorable conditions 

 they will be successful under a great range of conditions. The 

 great age to which trees often live and the slowness with which 

 they grow makes it possible for conditions to change while the 

 trees still live on with changes only in leaf structure. It is to 

 be expected that the distribution of animals is correlated with 

 the occurrence of seedlings or of quick growing plants or at least 

 with leaf structure types rather than strictly with species of 

 trees. These facts suggest that there are two types of cases 

 in which physical conditions and forest conditions are not in 

 accord. In the first case atmospheric conditions become favor- 

 able for forest animals before any w r oody plants have been able 

 to grow, in the second, woody plants remain after conditions 

 have become unfavorable for forest animals; both are due to 

 lagging behind of vegetation; both are very local and of minor 

 significance. 



A comparison of the data of Yapp (Table V.) and Transeau 

 (Fig. 6) shows a difference between the evaporation of the lower 



FIG. 6. Showing the comparative evaporation rates (c.c. per day) in the 

 ground stratum of several animal habitats on Long Island during July and August. 

 (After Transeau, courtesy of the Botanical Gazelle.) 



