360 BOTANICAL GAZETTE [NOVEMBER 
processes, but also for some of the elementary ones. The elemen- 
tary processes of growth itself (that is, the immediate phenomena 
which condition growth, the ones first met with in a rational 
attempt to analyze the complex process) are all or nearly all 
physical in nature, and not to be regarded as chemical. They 
include such physical changes as coagulation, precipitation, altera- 
tions in elasticity, swelling by imbibition and osmotic action, and 
many others. It thus becomes apparent that the reason why the 
chemical temperature coefficient appears to be manifest in growth 
phenomena cannot be that these phenomena are primarily and 
immediately chemical in their nature, but that, physical though 
they are, they depend in turn upon other internal changes that are 
unquestionably chemical. Thus, for a single example, the precipita- 
tion or coagulation of colloid material met with in the formation of 
cell walls in plants must logically be dependent upon the continuous 
presence of the precipitating substances in the peripheral layer of 
the protoplasm of each growing cell, and within a certain range 
of concentration, and this continuous presence indicates chemical 
processes which must be effective not very far back (in the chain 
of causally connected phenomena) from the precipitation itself. 
Under such circumstances it might be expected that a physical 
complex such as growth would frequently exhibit a chemical 
temperature coefficient. 
The fundamental physical changes which make up growth have 
not yet been studied sufficiently to permit the making of any 
estimate regarding the orders of magnitude of their temperature 
coefficients; nevertheless, we are certain that some of these coef- 
ficients possess values widely different from that postulated by 
the vAN’tT Horr-ArRHENIUS principle. Thus, for example, the 
temperature coefficient of osmotic pressure, within the range 
encountered in living cells, approximates the familiar quantity 
0.003665, as usually employed, for each single degree above the 
zero point of the Centigrade scale, the pressure at o° being taken as 
a basis. If the pressure at o° be considered as unity, the pressures 
at 4°, 14°, 24°, and 34° become 1.01466, 1.05131, 1.08796, and 
1.12461, respectively, and for each 10° rise in temperature the 
pressure is increased by only about 0.04. 


