ECOLOGICAL SUCCESSION. 83 



Some investigators have questioned the importance of vege- 

 tation to animals and we note here that the distributions 

 of plant and animal species are not always correlated. If one 



u 



FIG. 5. The bluff of Lake Michigan at Glencoe, III., showing several stages of 

 forest development. To the right of an imaginary line a-b are small areas of the 

 habitats shown in Table IV., in columns i and 2. Within the triangle a-b-c are 

 areas of the same habitat invaded by shrubs under which are found forest animals. 

 To the left of ac is an area of shrubs and saplings which has a full quota of forest 

 floor animals. (Reprinted from the Journal of Morphology.) 



refers to species of plants and species of animals then the vege- 

 tation very often is not correlated with the distribution of the 

 animals. If on the other hand one means that the plants are 

 controllers of physical conditions, then vegetation can be said 

 to be of very great importance. 



5. Stratification of Conditions. 



An inspection of the tables and the discussion following them 

 shows that different animals which do not burrow into the ground 

 inhabit different levels of the forest. For example Acrosoma 



