522 BOTANICAL GAZETTE [DECEMBER 
latter condition holds true also for the controls; containing only water, pyro- 
catechin, and plant material. Furthermore, if the Ch changes during the 
experiment and only the initial couichateation is determined, as in BUNZELL’S 
work, no very accurate conclusion can be drawn as to the effect of this factor 
on oxidase activity. 
BunzELt finds the inhibiting concentration for tulip tree material to lie 
between 1.58 and 5.02X10~3, and for the magnolia between 3.5 10~3 and 
8.91X10—4. He considers that his results show “that the acid sensitiveness 
figure is a rather fixed number for any particular genus.”’ He says also that 
it even seems “that the acid sensitiveness constant is the same or nearly the 
same for different genera (tulip and magnolia) of the same family (Mag- 
noliaceae).” An analysis of his table III shows in general that the less the 
natural acidity of the plant material the lower the Cy necessary to cause total 
inhibition of its oxidase activity. This relation does not seem to hold in all 
cases, possibly because the various degrees of acidity used were too far apart to 
establish the inhibiting concentration with any great degree of accuracy. 
If further work should prove such a relation general, new force will be 
added to the suggestions of BUNZELL and others that there is a distinct oxidase 
for each plant or group of closely related plants; not necessarily because they 
are protein in nature, however, as BUNZELL supposes. They may resemble 
each other in plants of the same family; they may show various properties of 
proteins, such as denaturing by acids, alcohol, and heat, and still be something 
quite different from proteins. BAYLIss suggests, on the basis of work by BACH 
and Cuopat and others, that oxidases are merely some form of iron copper ot 
manganese kept in a disperse condition by various colloids. If these colloids 
are proteins the action of acids, for example, removes them as dispersing 
agents and allows the oxidases to precipitate. As a result of absorption, the 
two may come down together as a single precipitate which gives both protein 
and oxidase reactions without ever having existed as a real compound in the 
living plant. Such a hypothesis, however, fails to apply to peroxidases, for 
these, according to BeHrinc, Aso, and BacH and CHoDAT, are very little 
affected by heat. Bacx and Cuopar also found that horseradish peroxidase 
when carefully purified contains no iron or manganese. 
In connection with BuNzELt’s “acid sensitiveness figure,” the question 
arises whether the inhibition he noted was all due to acidity. When a buffer 
solution of any sort is used to establish a definite hydrogen-ion concentration, 
elements are added which in the quantity used may be entirely foreign to the 
plant and productive of anomalous results. Illustrations of this are seen in 
Bunzetr’s table III. For example, extract of potato peeling with a natural 
Cn of 1.021076 (no buffer solution being present) caused 22 per cent more 
oxidation than the same extract when a buffer solution was present and the 
Ch practically the same (1.04X10~®). Even more marked are the results 
with potato sprouts, for with the Ch just about the same whether the buffer 
solution were present or not, they gave 16 per cent more oxidation without 
