PREFACE. XV 



importance and promise tor the future as we frankly do. Ecological 

 science has won its way in a comparatively short time, and now finds 

 itself in the front rank of those lines of intellectual effort that con- 

 stitute biology in the broad sense. Following Warming and Schimper, 

 the biological world has rapidly become very thoroughly interested 

 in the occurrence and behavior of organisms under natural conditions 

 and in the reasons for this occurrence and behavior. This widespread 

 interest may be taken as evidence that ecological study is now generally 

 regarded as fully as worth while as are taxonomy and phylogeny. 



Since ecological problems are dynamic ones by their very nature, 

 the quantitative aspect of ecological description and the dynamic 

 relation of different sets of conditions within and without the plant 

 must receive the main attention as soon as a superficial acquaintance 

 with the field has been attained. Plant geography can progress but 

 little farther by qualitative observational methods, and the physio- 

 logical and quantitative point of view must, of necessity, finally pre- 

 vail. Our aim has been largely to make some planned preparation for 

 this newer development, which has already gained considerable head- 

 way. 



Another and more obviously practical reason for regarding the 

 physiological ecology of animals and plants as of very great promise 

 lies in the fact that the art of animal and plant production (agriculture) 

 rests almost wholly upon this branch of biological science. The 

 problems with which the physiological ecologist deals are the same 

 problems as have to be solved by the agriculturist. One may study 

 natural vegetation or the distribution and environmental relations 

 of wild animals and the other may give his attention wholly to agri- 

 cultural crops and the rearing of domestic animals, but the problems 

 and the general methods by which solution may be obtained are the 

 same in both cases. The interpretation of crop production in terms of 

 climatological conditions has already attained to great importance. 

 The government of Russia long maintained an organization for the 

 study of agricultural climatology and the results warranted great 

 expectation. During the years in which we have been engaged upon 

 the present investigation, the Canadian government has copied many- 

 features of the Russian organization, and this branch of the Dominion 

 Meteorological Service is now well established. Finally, the obvious 

 importance of climatology in agriculture has been emphasized in the 

 United States through the establishment of a special division of agri- 

 cultural meteorology in the United States Weather Bureau. 



Also, it should be remarked that much of the art of forestry rests 

 upon the science of physiological plant geography; so much so that 

 students of forestry already clearly realize the need for studies of the 

 kind suggested by this publication. 



