2l6 
R. B. HARVEY 
inoculated with B. tumefaciens. Tissue dilutions representing the same 
green weight of material were made up to Ch 3-6 X io~^ and w/6o total 
salt concentration. Oxidase determinations were made in an oxidase 
apparatus which has been described in another place (lo) and which is a 
modification of the simplified Bunzell (ii) oxidase apparatus (12). After 
shaking for four hours at a constant temperature of 30.2° C, the following 
readings were given as the average of three determinations : 
In this case it appears that the oxidase activity in the tumored areas 
is greatly increased. An increase in oxidase activity in tumored tissues 
has been reported in a number of articles (22). 
In this connection it is interesting to note that the anthocyanin color 
is greatly increased in the tumored areas of Bryophyllum leaves induced by 
freezing, so that the intumescences stand out as red areas. The intumes- 
cences are produced mostly along the veinlets rather than in the vein islets. 
The deepest color of anthocyanin is located along the veinlets within the 
intumescences. 
When Bryophyllum leaves are frozen in spots over a small percentage of 
the area, the frozen spots turn brown. One can predict from the depth of 
this brown color whether the area will die or will be stimulated to growth. 
As the percentage of the total area which is frozen increases, the depth of 
brown color in the spots decreases. When the whole leaf is frozen the color 
is uniformly distributed. If brown-spotted leaves are killed by freezing or 
by ether, the spotted areas maintain the deepest color, showing that the 
oxidizable substances have been partly removed from the surrounding 
tissues. It appears from this that there is an accumulation of the colored 
compounds within the frozen areas. This becomes very marked about 12 
hours after freezing, as shown in the photograph (fig. i). The greatest 
development of color occurs along the veinlets within the frozen areas 
(fig. 2). The frozen areas seem to have the property of taking up sub- 
stances from the surrounding tissues which are converted within them and 
which accumulate as brownish colored compounds. Onslow (13) has given 
us data on the nature of such substances. Substances of the type of catechol 
occur in plants which brown on injury. Peroxidase activates the oxidation 
of these aromatic compounds, and the oxidized product is an organic 
peroxide. 
Oxidase activity of beet tissue 
Tumor tissue 
Hydrochinone 
Pyrogallol . . . 
3.24 cm. Hg. 
4.14 cm. Hg. 
Healthy tissue 
Hydrochinone 
Pyrogallol . . . 
0.90 cm. Hg. 
. 1.70 cm. Hg. 
