FORMATION OF OVERGROWTHS 
217 
It has been shown by Krassnosselsky (14) that an increased rate of 
respiration follows frost injury. The author so far has not been able to 
Fig. I. Development of color in Bryophyllum leaves as a result of freezing. Notice 
the deep color in the small isolated frozen areas and the decrease of the color intensity 
with increasing size and frequency of the spots. The leaf with uniform color distribution 
was frozen throughout. 
compare the respiratory rate of the frozen and normal areas. It would be 
desirable also to determine the oxygen acceptors in these spots. There is 
no immediate increase in the catalase activity of the areas frozen, nor does 
this increase until growth can be observed. Blackening indicates that there 
is an abnormally oxidized condition in the frozen areas. 
Discussion 
To the author it seems plausible that the hydrogen-ion concentration of 
the cell sap in the frozen areas may be decreased by removal of H+ during 
