XIV PREFACE. 



sidered, but, rather, simply to describe some of the vegetational and 

 climatic features of the country, in such a way as to emphasize the 

 desirability of pushing this sort of study forward, and to make clear 

 what sort of observations and what sort of deductions therefrom seem 

 to give promise in this direction. Our work is primarily descriptive, 

 as most ecological work must be for a long time to come, and the dis- 

 covery of simple concomitancy is our nearest approach toward the 

 establishment of causal relations. We have been led to the view that 

 ecological science can be most rapidly advanced through this general 

 method of quantitative comparison and by the placing upon record of 

 such cases of concomitancy (between plants and their surroundings) 

 as this method is able to bring forth. 



Our attitude toward plants has been that of the physiologist, and we 

 have tried to bear constantly in mind the conception that vegetational 

 characters are simply expressions of the activities of individual plants. 

 We maintain that all discovery of true causal relations in ecology must 

 depend finally upon this point of view. Our attitude toward cUmatic 

 conditions has been somewhat, though not wholly, like that of the 

 climatologist ; with meteorology and the causes of climatic features 

 we have had nothing to do. Attention has been centered, as far as 

 possible, upon those particular climatic features that directly affect 

 plant activity. Thus most of our climatic discussions bear either 

 upon temperature or moisture conditions. We have tried to consider 

 climate in relation to plant growth in much the same way as the 

 experimental physiologist considers the relations between his cultures 

 and their surrounding conditions. 



Many features of the vegetation and many climatic conditions have 

 been omitted or have received scant consideration in the present 

 publication. Those have been more seriously considered which seemed 

 to give the greatest promise and for which the needed data were most 

 readily available. The work has grown from very unpretentious 

 beginnings made over a decade ago, and its ramifications into aspects 

 not at first thought of have been controlled partly by a priori judgment 

 as to what appeared more or less promising, partly by availability of 

 the requisite observations and partly by our own limitations as to 

 time and energy as well as ability. Many other features or dimensions 

 of climate and of vegetation might have been dealt with, and the reader 

 will find here many suggestions for investigations, the carrying out of 

 which would require from a few hours to many years. In short, em- 

 phasis should be laid on the fact that the present study is to be regarded 

 only as a beginning along a line that holds forth very great promise. 

 The real conclusions from our work are to be drawn by others as this 

 kind of study is pushed forward. 



It may be in place here to give a little space to our reasons for 

 attributing to quantitative physiological plant geography such great 



