THE AUXO-THERMAL INTEGRATION OF CLIMATIC 
COMPLEXES! 
D. T. MacDougal 
Some features of the life of a plant depend so largely upon a simple 
» and uncomplicated enzymatic action, oxidation or other form of energy 
release, reduction, absorption or hydratation that their course may 
run parallel to that of a reaction the velocity of which is known and 
expressible by exponential law. As examples of this may be cited the 
development of buds or the germination of seeds in which the hy- 
drolysis of accumulated food-material and the measurable develop- 
ment ensue at a rate in accordance with van't Hof's rule by which the 
velocity increases two or three times with every rise of temperature 
of i8° F.2 
Many of the more important activities of living matter, however, 
are the combined expression of a complicated group of reactions, in 
which the initiating temperature, and the acceleration above it are 
not identical or parallel, and these may be linked with still others 
which are not a function of temperature. 
It follows therefore that the resultant may be one not calculable 
from known data concerning reaction velocities. This is true of 
growth, differentiation and of the constructive processes in general, 
both in a morphogenic and physiologic sense. 
It is obvious that if we are to make any rational interpretation 
of the entire effect of temperature upon the organism in any phase of 
its activity, or during all of its ontogeny a method must be formulated 
by which the effect of the duration and intensity of the temperature 
exposure upon the organism may be calculated. Now since this may 
not be done in terms of the reaction velocity of any of the underlying 
or component chemico-physical activities our only recourse is to use a 
resultant standard, one derived from the organism itself. In other 
^ Paper read in the Symposium on "Temperature Effects" before the Botanical 
Society of America at Atlanta, December 31, 1913. 
2 See Drinkard, Fruit-bud Formation and Development. Ann. Rep. Va. Poly- 
tech. Inst. Agr. Exper. Sta. 206-212, 1909 and 1910, as an example of the application' 
of physio-chemical constants to developmental processes. 
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