304 BOTANICAL GAZETTE [OCTOBER 
prove harmful, and its destruction by catalase would not only 
prevent injury, but the oxygen liberated would be used again in 
respiration. 
UsHErR and Priestty’° believe that hydrogen peroxide is formed 
in relatively large amounts in photosynthetic processes, and that 
its decomposition by catalase prevents it from reaching a sufficient 
concentration to bleach the chlorophyll. 
On the other hand, SHAFFER’ considers that the decomposition 
of the peroxide is of advantage principally in checking oxidation 
processes, basing his theory on the fact that the oxygen liberated 
from the decomposition is a poorer oxidizing agent than the hydro- 
gen peroxide. In this connection BATTELLI and STERN’ state that 
catalase retards the oxidation of ferrous sulphate in the presence 
of animal tissue. 
There is very little experimental evidence, however, to indicate 
that hydrogen peroxide is actually produced in living tissue, except 
under specialized conditions. Moreover, it seems to be not particu- 
larly toxic, since the writer has found that wheat, rice, and radish 
seedlings develop without ill effects in as high concentrations as 
©.5-1 per cent. The hypothesis that catalase is of advantage in 
checking oxidations is also largely invalidated by the observation 
of Bacu and Cuopar?’ that catalase acts only on hydrogen peroxide, 
and not on organic peroxides or on the oxygenases; for it is these 
oxygen compounds rather than hydrogen peroxide that are con- 
cerned in respiratory oxidations. The writer has found also that 
while colloidal platinum decomposes hydrogen peroxide, it has no 
action on the oxygenases. An extract of the outer tissue of potatoes, 
which exhibits an active oxygenase in its direct action on gum 
guaiac (free from peroxide), was shaken for some hours. with 
colloidal platinum, but after removing the platinum by filtration” 
6 Usner, F. L., and Prrestty, J. H., Proc. Roy. Soc. London 77:369-376, 78: 
318-327. 
7 SHAFFER, P. A., Amer. Jour. Physiol. 14: 299-312. 1905. 
8 BATTELLI, F., and STERN, L., Compt. Rend. Acad. Sci. 141:916-918. 1904. 
® Bacu, A., and Cuopat, R., Ber. Deutsch. Chem. Gesells. 37: 1342. 1904. 
” This sample of colloidal metal could be removed from its solution by passing 
through a hard filter paper; this is shown by the fact that the filtrate from a watery 
suspension had no action on hydrogen peroxide. 
