1884.] and on the Assimilation of Carbon. 341 
molecule of a body is, so to speak, attuned to a certain 
number of vibrations, and when it is struck by light waves, 
vibrating in unison with it, these waves give off their vis viva 
to the molecule, the light is absorbed, and its vis viva per- 
forms chemical work. As, however, the number of vibra- 
tions plays a certain part in chemical adtion, as is proved by 
the behaviour of silver chloride with the violet rays, it is 
possible that the rays of shorter undulations are of im- 
portance in the process of assimilation. Hence Lommel’s 
conclusion that the maximum of assimilation coincides with 
the maximum of absorption I. can only be regarded as a 
probability resting on theoretical considerations. 
Prof. Hoppe-Seyler has also pointed out that emissions 
and absorptions of light are effected not by the entire mole- 
cule, but by atoms and groups of atoms. As the greatest part 
of the sunlight which impinges upon a solution of chloro- 
phyll is converted into red fluorescent light of the wave- 
length of the spedtral region between B and C, the atomic 
group which emits this fluorescent group must be freely and 
widely movable. The supposition lies, therefore, near at 
hand that it is this atomic group which splits off oxygen in 
the living plant. 
Experiment, alone, however, is entitled to give a valid and 
final answer to this question. Assuming that the liberation 
of gas by Elodea Canadensis gives an expression for the in- 
tensity of assimilation, Dr. Reinke shows that the maximum 
of assimilation lies between B and C, falling off very ab- 
ruptly towards the less refrangible side, and also, though 
more gradually, on the refrangible side. In the less refran- 
gible portion of the spedtrum the curve of assimilation runs 
almost parallel with the curve of absorption if we overlook 
the two smaller maxima of absorption II. and III., which 
latter seem to be as unimportant for the decomposition of 
carbonic acid as is the absorption in the violet ray. The 
author arrives, therefore, at the following conclusion : 
Assimilation appears, in accordance with the corresponding 
course of the curves, to be a function of absorption in that 
atomic group in chlorophyll, and in all its more immediate 
products of decomposition readily absorbs the rays between 
B and C, and in a dissolved state emits rays of the same 
wave-length as fluorescent light. 
Dr. Reinke gives a theoretical explanation of this experi- 
mental fadt. He holds that the atomic group (7) of chloro- 
phyll, on the adtivity of which depends the decomposition 
of carbonic acid, is inclined to oscillate with the velocity of 
440 to 450 billions per second, and is most readily set in 
