1913] LIVINGSTON—TEM PERATURE COEFFICIENTS 373 
What may be the meaning of this new kind of climatic chart, as 
regards vegetational distribution, plant activity, or any other 
phenomena influenced by climatic conditions, cannot yet be sur- 
mised, but the chart does indicate a very important truth as far 
as climatology and climatological methods are concerned. If we 
look upon the normal daily mean temperature as in some way 
involving a criterion for the approximate evaluation of the naturally 
effective heat supply, it is shown that the summation of these nor- 
mals for the period of the frostless season does not give, excepting 
in a very superficial way, the same chart for the United States 
as does the corresponding summation of temperature efficiencies 
following the assumptions here made. 
It may be said that the direct index is a measure of one dimen- 
sion of the temperature factor of a climate, while the efficiency 
index as here employed measures another dimension. Which of 
the two dimensions more nearly approximates the measure of the 
temperature effectiveness of a climate, as far as plant growth is 
concerned, will no doubt remain for a long time undetermined. 
The present independent status of the direct summation method 
for the treatment of temperature data rests upon phenological 
observations in the open, while the status of the other method of 
treatment (employing temperature efficiencies instead of the daily 
mean temperatures themselves) is founded upon deductions from 
the chemical velocity coefficient of van’t Horr and ARRHENIUS, 
upon physiological experimentation under more or less controlled 
conditions, and upon the fact that all physiological processes are 
chemical in their nature or else depend upon other processes which 
are chemical. It must be admitted, on physiological grounds, that 
some sort of efficiency summation seems likely to prove more 
truthful and more valuable in vegetational-climatic studies than 
the direct summation of temperatures. The latter method of treat- 
ment has no a priori or logical basis (although, as has been seen, 
it is not altogether without pragmatic or empirical points in 3% 
favor), and appears, superficially at least, to be quite arbitrary in 
its theoretical conception. 
The details of the distribution of our various ratio values deserve 
attention, for they bring out quite unequivocally, not only that 
