370 F. E. CLEMENTS SIGNIFICANCE OF PALEO-ECOLOGY 



makes it clear that living things and processes are to be studied first and 

 last in the oikos, or habitat — whether forest, prairie, desert, or cultivated 

 field — though with the fullest use of controls wherever these are necessary 

 or desirable. Finally, the method of the ecologist must be at the same 

 time intensive and extensive if he is to follow processes accurately and to 

 apply them broadly. 



The Utilization of Ecology 



It is perhaps puzzling to understand how the demands of ecology can 

 be met in a field where processes have ceased. The readiest answer, and 

 a fairly complete one, is afforded by the principle of uniformity of proc- 

 esses, the use of which has made modern geology possible. The value of 

 this principle has recently been recognized in climatology, and it is also 

 proved to be of wide application in plant succession. The initial use of 

 it in succession has met with such success as to suggest its wide applica- 

 tion in the whole field of paleo-ecology. As a consequence, it has become 

 clear that the development of the ecological aspects of paleontology must 

 depend absolutely on the progress of present-day ecology. In just the 

 degree that the latter becomes s}TLthetic, experimental, and cpiantitative 

 w^ill it be possible to aj^ply it accurately and thoroughly to the interpre- 

 tation of past life processes. In this connection there is no thought of 

 minimizing the ecologic contributions of paleontology; but these have 

 usually been a by-product of taxonomic, phylogenetic, or stratigraphic 

 studies, and their ecological orientation has been difficult or uncertain. 



Synthetic Character of Paleo-ecology 



It is assumed that paleo-ecology must be primarily synthetic : that it 

 must deal chiefly with processes, their development and correlation. In 

 fact, the latter stand out in bolder relief because th% i^henomena are 

 fcAver and more isolated. Moreover, special fields have not been differen- 

 tiated in it, and it is possible to follow sequences through without stop23ing 

 at artificial boundaries. This is especially significant at a time when the 

 conviction is slowly growing among ecologists that the life of a habitat 

 must be studied as a unit complex and not in two detached parts. The 

 feeling that correlation is the paramount method leads to the realization 

 that it must be based on natural and hence causal sequences. This is 

 what is meant by saying that the clue to ecology is found in the habitat. 

 The latter is the complex of causes or of factors which act on the plant 

 and the animal: but the habitat acts directly on plants. Avhile it affects 

 land animals for the most part indirectly through the food and shelter 

 control exerted by plants. As a consequence, the plant may be looked on 



