INTRODUCTION. 5 



that the Latin name is a convenient means of expressing genetic rela- 

 tionship, that it is a convenient designation for speaking about species 

 in any connection whatever, and that it will continue to have these uses 

 even after the student of genetics has been driven to use some numeri- 

 cal scheme of designation for the forms in which he is particularly- 

 interested. Nevertheless, in order to come squarely to face with the 

 problems of physiological plant geography, we shall have to lay aside 

 much that floristics has taught us, and shall have to ignore phylogeny, 

 except in so far as it shows us that plants of close kinship often have 

 the same or similar anatomical and physiological characteristics. The 

 first writer to insist upon the physiological point of view in plant 

 geography was A. F. W. Schimper, whose monumental Plant Geog- 

 raphy, which appeared 22 years ago, has done much to stimulate 

 interest and activity in what we may designate as eausational or 

 etiological plant geography. 



We have approached our problems in plant geography with the men- 

 tal conception that they are merely problems in physiology, with all 

 of the environmental conditions fluctuating and uncontrolled, but 

 nevertheless measurable, and with all the activities of the plant in 

 normal performance and also measurable, not by auxograph and bal- 

 ance, but by such features as distributional extent, habitat occurrence, 

 communal behavior, relative abundance, size, seasonal behavior, etc. 



The observation, description, and classification of the innumerable 

 types of vegetation which clothe the earth have been carried on in great 

 detail for some of the areas of Europe, Africa, and North America, 

 and have been outlined for the whole globe. These observations and 

 descriptions range from the hasty and incomplete work of pioneer 

 explorers, who were perhaps making many kinds of observations at 

 the same time, to the most painstaking charting of the location of 

 individual plants over larger or smaller areas. The classification of 

 plant communities from non-floristic standpoints has been made, in 

 connection with their description, by numerous workers in many 

 countries, and almost innumerable schemes of vegetational classifica- 

 tion and nomenclature have been proposed for general application. 



The fundamental defect of these attempts at the classification of 

 such a complex body of material is that they are all largely subjective 

 in character. As a result of this, the total amount of disagreement 

 among students of vegetation is at least as great as the amount of 

 agreement. Perhaps no ten workers could be found all of whom would 

 place the same plant community in the same general vegetational 

 category or would propose less than 6 or 8 different technical designa- 

 tions for it. There is a strong desire among all classes of plant geog- 

 raphers to come into closer agreement in these matters, but it may 

 well be asked whether, in default of fundamental and universal criteria 

 of classification, such agreement is possible among men of different 



