19 20] CURRENT LITERATURE 357 



of yeast cells. When possible they used the potassium permanganate titra- 

 tion method for determining catalase activity. In cases where additions of 

 thymol, glucose, etc., rendered the permanganate method inaccurate, the 

 volumetric method was used. They used mainly their cultures of distillery 

 top yeast S.B. II. Some experiments were run with brewery bottom yeast. 



ME 



enzyme 



The reaction is one of the first order. The reaction constant increases in 

 proportion to the amount of yeast. Small amounts of protoplasmic poisons 

 (toluol or chloroform) raise the catalase activity of these cells 6-fold. When 

 cells were dried in the air or otherwise without injuring them, the catalase 

 activity rose 1 0-15-fold. When emulsions of the yeast were heated 0.5-2 

 hours at 55-63 C, the catalase activity rose 20-30-fold. The activation by 

 heating is greatly influenced by reagents in the emulsion at the time of heat- 

 ing. Similar activation of catalase has been demonstrated in a number of 

 other micro-organisms. The catalase activity of yeast can be raised by 

 previous treatment with sugar solutions. This increased catalase activity is 

 not due to increased permeability of the cells to catalase, but is an activation 

 within the living cells. The reaction constant is not a measure for the catalase 



* 



content of the cells.— Wm. Crocker. 



Parasitism. — Hawkins and Harvey 15 have made an interesting study of 

 the nature of the resistance of White McCormick tubers to the tuber rot 

 caused by Pythium debaryanum Hesse. The White McCormick is very 

 resistant to the disease, while Bliss, Triumph, and Green Mountain are very 

 susceptible. From their experiments they think it probable that the fungus 

 enters the cells of the potato by mechanical puncture of the cell walls and not 

 by enzyme action. The McCormick is less susceptible to the disease than 

 the other varieties, because its cell walls are more resistant to this mechanical 

 puncture. Determinations of the pressure required to puncture the cell 

 walls give much higher results for the McCormick than for the susceptible 

 varieties. The rate of growth of the fungus is much slower in the McCormick. 

 Correlated w r ith the greater resistance of the McCormick is a higher crude 

 fiber content. If its osmotic pressure is to be considered the force available 

 to the fungus for this mechanical puncture of the cell walls, then the cases of 

 resistance of the potatoes used in the experiments would be explained, with 

 three exceptions. — S. V. Eaton. 



Correlations. — Child and Bellamy 16 have done a very interesting piece 

 of work on correlations in plants. They can break up correlation effects by 



15 Hawkins, L. A., and Harv 



Pythium debaryanum Hesse on 

 P ls * 35-37- figs. 2. 1919. 



potato tuber. Jour. Agric. Res. 18:275-297. 



16 Child, C. M., and Bellamy, A. W., Physiological isolation by low temperature 

 in Bryophyllum and other plants. Science 50:362-365. 1919. 



