1917] CURRENT LITERATURE 521 
tendency there may have been in textbooks to present BAYER’s hypothesis as 
representing facts. 
ey discuss the theories and suggestions of four men: (1) the well known 
theory of BAYER involving formaldehyde as an intermediate product; (2) the 
suggestion of vAN’T Horr that assimilation consists of two parts, a photo- 
chemical reaction and an enzyme reaction; (3) SIEGFRIED’s suggestion that 
carbon dioxide may form carbamino groups with the protoplasm of the plant 
cell and that the photochemical reaction may then occur in a complex carbon 
compound; and (4) WiitstATrerR’s theories which, so far as they are new, are 
regarded by the reviewers as rather wild, the most reasonable one suggested 
by him being merely a repetition of SIEGFRIED’s suggestion. 
In the end it appears that we have at present no satisfactory theory of 
the changes that take place between the entrance of CO, into the plant and 
the production of carbohydrates. 
Although deploring the lack of coordination among the various workers, 
and the tendency of botanists to accept without question the suggestions of 
physicists and chemists as to the nature of plant processes, the reviewers con- 
clude that plant physiology is developing into an exact science, utilizing the 
experiences of the fundamental sciences, physics and chemistry, but having 
working principles and methods of itsown. That it will thus be of great service 
in plant production requires no prophetic vision.—GrEorGE B. Rice. 
Studies on oxidases.—In connection with his work on plant oxidases, 
BuNzELL’ has published results of an investigation of the effect of hydrogen- 
ion concentration, Ch, on oxidase activity. Using his own simplified oxidase 
apparatus to measure oxidation and the gas chain to measure hydrogen-ion 
concentration, he finds that the oxidase activity of several kinds of material 
from potato tubers is completely inhibited by a Cn of 2.0-2.8X10—4. The 
various concentrations were obtained by adding sodium hydroxide and acetic 
acid in various Ae ng or either one alone, to mixtures of the plant 
material and pyrocatec 
It is worth noting ae that the two together constitute a true buffer solu- 
tion capable of maintaining a fairly constant hydrogen-ion concentration, but 
that neither one alone suffices. Consequently, if there is a tendency for the 
acidity to increase in the Bunzell apparatus, as suggested by Rose® in 1o15, 
conditions are not comparable in the different mixtures. Those containing 
the true buffer solution will have practically a constant Cp throughout the 
course of the experiment, while those containing only sodium hydroxide or 
acetic acid will have a Cp which is larger at the end than at the beginning. The 
7 BuNZELL, H. H., The relationship existing between the oxidase activity of plant 
juices and their hydrogen-ion concentration, with a note on the cause of oxidase activ- 
ity in plant tissue. Jour. Biol. Chem. 28:315-333. 1916. 
8 Rose, D. H., Oxidation in healthy and diseased apple bark. Bor. Gaz. 60: 
55-65. 1915. 
