EN V IRONIC FACTORS w 



exhibited by the beetles in Professor Tower's experiments, and steps are 

 now being taken for the necessary analytical tests for the standardiza- 

 tion of temperature effects in terms of protoplasmic activity. 



Another phase of temperature effects — concerning energy release in 

 protoplasm — has been studied by Professor Ellsworth Huntington, whose 

 analysis of the records of piece-workers in factories established the fact 

 that the least amount of work is accomplished with open air temperatures 

 below the freezing point and in the neighborhood of zero Fahrenheit. 

 The amount increases slowly, however, up to 28° F., then rapidly to 38°, 

 slowly to 48° and more slowly to the optimum of 58° F., above which 

 the rate and amount declines as the weather becomes warmer. It may 

 seem a far cry from the growth of a wheat plant in California to the 

 muscular action of a factory operative in New England, but both are 

 directly dependent upon the fundamental characters of living matter, 

 especially in its relation to temperature. 



The distribution and grouping of organisms on the world's surface 

 is conditioned by the agencies which participate in moving them from 

 place to place and by the presence of conditions suitable for their sur- 

 vival and existence. If all species inhabited every place suitable for 

 them, geography, so far as vegetation is concerned, would be a subject 

 about which many closed chapters might be written. They do not, how- 

 ever, as they have not been carried to all the places in which they might 

 survive, and secondly, the conditions comprising the environic complex 

 are slowly but surely changing, reversibly or irreversibly, practically 

 everywhere on all land surfaces. Under such conditions the dynamics 

 of plant geography assumes an importance not yet realized. 



So far we have discussed the results of analyses of our plantations 

 and experimental settings. The geographer, however, needs to have de- 

 fined for him the principles governing the variations in the various 

 environmental components and of course temperature is an agency 

 which has been drawn upon to account for some of the major features 

 of distribution in geologic as well as present time. Methods and prac- 

 tises that have become conventionalized estimate temperatures by alti- 

 tude and latitude, the actual data obtained by instrumentation being 

 compiled as mean temperatures, and the averages of maxima and min- 

 ima. I need but to refer to the measurements of temperature in terms 

 of growth discussed previously to illustrate the inadecpiacy of these data 

 for agricultural operations. 



The obvious and popularly accepted assumption that low valleys are 

 warm and that ridges are cold wind-swept habitats, arising from the 

 conception of surface temperatures as in the main a function of altitude 

 has been followed much too far, and the geographer who bases his gen- 

 eralizations on assumptions of this kind will be due to encounter some 

 extremely disturbing anomalies, some of which have come in for exami- 

 nation and measurement at the Desert Laboratory by Dr. Shreve. 



