262 LIVINGSTON— CLIMATIC AREAS [April .8, 



of plants and animals which thrive there. The sage-brush is a plant 

 with physiological characters such that it thrives best in the tem- 

 perate arid regions of North America, and the climate of these 

 regions is such as to render sage-brush the dominant and character- 

 istic form of plant life. So we reason in a circle and arrive nowhere. 



There are, however, instrumental methods more ideal, if not 

 more satisfactory, by which climates may be compared. Thus the 

 averages or means of temperature, precipitation, humidity, etc., of 

 the meteorologists and climatologists, give numerical data which are, 

 in a way, descriptive. It appears, indeed, that means or averages 

 of the climatic data which have been and are being accumulated 

 throughout the world should furnish a numerical basis for distin- 

 guishing between different climatic areas, and this basis has of 

 course been employed by climatologists for many years. Ecologists 

 and agriculturists have frequently made use of such climatic means 

 and have so described the climates with which they have had to deal. 

 But if you will look over any of the recent ecological papers you 

 will find that the definition of climates has not gone very far. 

 Usually a section of such a paper is devoted to the characterization 

 of the climates of the areas considered, but the quantitative part of 

 this section is little more than a mass of unrelated figures ; out of 

 these the author himself seems to make no serious attempt to draw 

 generalizations that may be related to the corresponding vegetational 

 areas. 



We are thus confronted with a state of affairs which is far from 

 satisfactory. The weather services of the world are expending vast 

 amounts of wealth and energy in accumulating, year by year, obser- 

 vational statistics bearing upon the various climatic areas. These 

 statistics are largely used for weather prediction and for the pur- 

 poses of theoretical meteorology. It seems that quantitative climatic 

 descriptions must lie hidden somehow in these enormous masses of 

 figures, but the plant geographer, whether agriculturist or ecologist, 

 has thus far been able to derive therefrom but a very small amount 

 of applicable information. 



It seems to me that the reason for this state of affairs is a double 

 one : first, the climatological observations of our weather services 



