VOLUME LXXIV NUMBER 4 
THE 
BOTANICAL GAZETTE 
December 1922 
ECOLOGICAL FACTORS IN REGION OF STARVED 
ROCK, ILLINOIS 
CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 299 
FRANK THONE 
(WITH FIVE FIGURES) 
Introduction 
The work of Cow tes (5) in calling the attention of the then 
newly differentiated science of plant ecology to the concept of plant 
associations as stages in successions, not as entities complete and 
final in themselves, but rather as steps in the evolution of social life 
in the plant world, was of far reaching influence in determining the 
development of ecology in America as a dynamic science, as the 
study of a progress rather than as a mere set of methods for 
the description of.states. CowLrs was also the first to emphasize 
the importance of topography as a general control over other 
factors that directly influence the activities of plants. 
The earlier work in this field contented itself with pointing 
out the general effects of topography as a modifier, within a given 
region, of the climatic factors. It indicated the direction of such 
modifications, but only estimated their extent; it was qualitative 
rather than quantitative. It was, however, only natural that as 
time passed students of ecology should desire to gain a more exact 
knowledge of the factors controlling plant communities and their 
development, and a good share of the work now being done in Ameri- 
345 
