1884.] 
as affected by the Intensity of Light. 75 
concentrated light of the focus of a burning-glass, the evo- 
lution of gas goes on at its ordinary maximum rate until the 
injurious addion of the light becomes manifest and the 
chlorophyll is destroyed. 
As regards the theory of the addion of light, Herr Reinke 
deduces from his researches the following conclusions : — 
He believes that the liberation of gases observed in his ex- 
periments is an approximately accurate standard for the rate 
of the elimination of oxygen, and may thus again serve as 
an approximate expression for the decomposition of carbonic 
acid. He considers that the consumption of oxygen in the 
green cell vanishes in comparison with the liberation of 
oxygen. This fails to hold good at low intensities of light 
only when the proportion between the oxygen produced and 
consumed is different. 
The fadd that in intense and increasing light the liberation 
of oxygen remains constant in quantity, remains to be 
examined in the light of the various theories concerning the 
modus operandi of chlorophyll. 
According to one view the chlorophyll adds physically as 
a proteddive screen during the decomposition of carbonic 
acid. It is here assumed that an increased oxidising addion 
of the oxygen proceeds parallel with the growing intensity 
of the light. As now the above experiments prove that even 
in the most intense light there is neither an increase nor a 
decrease of the liberation of gas, we must suppose either 
that (1), with the increasing intensity of light, the decom- 
position of carbonic acid and the oxidation increase exaddly 
proportionally, which, considering the complete mutual in- 
dependence of the two processes, is little probable, especially 
as such a conneddion certainly does not appear during a de- 
crease of the intensity of light ; or (2), we must assume 
that the curve of the intensity of oxidation is quite different 
from that of reduddion, so that in the intense light the 
former diverges much from the latter, and that therefore the 
gas which is given off in the most intense light contains an 
increased proportion of carbonic acid. 
Herr Reinke has submitted this consequence of the latter 
assumption to an experimental test. He colledded the gas 
which was given off in i£ hours from Elodea sprays exposed 
to an intensity of light between 64 and 300 times that of 
ordinary sunlight. The temperature of the water had risen 
during the experiment from 20° to 29 0 C., and at the conclu- 
sion the two upper sprays, which had been most intensely 
illuminated, were completely bleached, whilst the others 
remained perfeddly green. The colledded gas amounted to 
G 2 
