FORMATION OF OVERGROWTHS 
suspension of the bacteria into the leaves by means of vacuum. This 
produced rather large tumored areas. Healthy leaf tissue which showed 
no tumor formation was taken from the same leaf. Three and three tenths 
grams of tumor and healthy tissue were diluted to 50 cc. after treating as 
before. Twenty-five cc. of these dilutions gave in the same time for tumor 
tissue 38.9 cc. O2; and for healthy leaf, 2.4 cc. of oxygen. 
Intumescences were also induced on Bryophyllum leaves by freezing 
the plants at a temperature of — 2° C. After about 15 minutes it was 
observed that frozen areas appeared over the surface of the leaf. The 
plants were removed from the cold chamber when the areas were about 5 
mm. in diameter and placed in the greenhouse. After five days the areas 
had grown into small intumescences. While these were still actively 
growing, leaves were selected in which the tumors formed about half the 
area. It was found impossible to get a greater percentage of the area to 
grow out as intumescences because death occurred if more than about half 
the leaf surface was frozen. The tumor spots were so small and so inter- 
mingled with healthy tissue that a quantitative separation of the tumored 
and healthy areas could not be made without introducing great error. 
Six grams of leaf tissue of which the tumored areas were estimated to 
represent half the tissue were taken and compared for catalase activity 
with 6 grams of normal tissue from a leaf of the, same age and size from the 
same plant. The tissues were ground with quartz and excess CaCOs and 
made up to 200 cc. Twenty-five cc. of the dilution were taken with 5 cc. 
of the hydrogen peroxide. After 15 minutes the following amounts of 
oxygen were evolved : 
Tumor 50 percent 3.1 cc. O2 
Healthy tissue 1.05 cc. O2 
Tissues of beet in which the overgrowths were produced by inoculation 
with B. tumefaciens gave on treatment in the exact manner given above for 
Ricinus tissue: 
Tumor tissue 8.1 cc. O2 8.9 cc. O2 
Healthy root tissue 5.6 cc. O2 5.4 cc. O2 
It should be noted that the increase in catalase activity of the intumes- 
cences produced no Bryophyllum leaves by Bacterium tumefaciens is much 
greater than that of the intumescences produced by freezing. 
The peroxidase and catalase activities in intumescences of cabbages 
induced by freezing are greater than those in normal tissues of the same leaf. 
Since this decrease in H+ concentration increases the catalase activity, it 
is interesting to note that the catalase activity is greatly decreased in mosaic 
leaves of tobacco which show greater H+ concentration than healthy leaves. 
In this case also, the Ph values are but slightly different, yet it appears of 
great physiological importance for the growth of the mosaic-diseased cells. 
The oxidase activity of tumor and healthy tissue was obtained on beets 
