34 2 Oy> the Chlorophyll of Living Plant-Cells . [June, 
motion by rays of this rate of vibration, whilst rays of either 
greater or less refrangibility do not produce this result. 
Assimilation, therefore, is a function of the undulatory 
power of the atom in the atomic group, and of the chloro- 
phyll molecule, — that is, of its chemical activity. As it is 
also a function of the light-rays of that number of oscilla- 
tions which can set this atomic group in motion, we may 
say that chlorophyll assimilates the vis viva of light, trans- 
forming it immediately into atomic vibrations, on the energy 
of which the splitting up of the carbonic acid depends ; the 
chemical work of the reduction process is only indirectly 
supplied by light. 
We may conceive that the vibrations of the atomic 
group y are not first produced by light, but that they take 
place also in the dark, though of too small amplitude to 
effeCt the work of assimilation. Light increases this ampli- 
tude, and is a condition even for the smallest decomposition 
of carbonic acid. The result of the chemical process in- 
creases then in proportion to the increase of the intensity of 
light up to a maximum value of the vibratory amplitude, 
which cannot be further augmented by an increased illu- 
mination. 
Whether the chemical aCtion of the group 7 in the process 
of assimilation is direct or indirect, is not decided by what 
has gone before. That the latter alternative is possible ap- 
pears from the researches of M. Becquerel, which prove a 
very interesting indirect aCtion of chlorophyll. Whilst silver 
chloride is decomposed only by the so-called photographic 
rays of sunlight, M. Becquerel observed, in a mixture of 
silver chloride with chlorophyll, the separation of metal in 
those parts of the speCtrum which correspond to the 
absorption-bands of chlorophyll. 
Dr. Reinke further discusses the relation of assimilation 
to fluorescence, and puts forward the view that we have here 
two reciprocal phenomena which may even be mutually ex- 
clusive. The green cell would not assimilate if its chloro- 
phyll was fluorescent. Fluorescence occurs with great 
motility of the chloroform molecule in solution. In solid 
chlorophyll the transformation ensues in another direction, — 
that is, in the reduction of carbonic acid, when the chloro- 
phyll occurs in the living cell, and when carbonic acid is 
present. 
