1919] 



WEBB — SPORE GERMINATION AND H ION CONCENTRATION 



205 



of 1 gm. KH 2 P0 4 , 3 ems. NaN0 3 , .5 cm. MgS0 4 , 100 cms 



sucrose in 1 liter water, and on the 

 hydrogen ion concentration to be 2 X 10 



•2 



enth day found the 

 Thev comment unon 



Waterman's estimate that the critical limit for P enicillium 



\icum is about 



-5 



-5 



N. H. and for Aspergillus niger about 

 4.5X10"° N. H. The reviewers think that the only explanation 

 for such discordant results must lie in a confusion in the 

 method of expressing hydrogen ion concentration. 



Fred and Loomis ('17) found that a mannitol solution with a 

 neutral reaction gave the highest count of B.radici cola from alfalfa. 



The addition of small amo 

 alter the number of bact 



of alkali did 



appreciably 



acid in equivalent 



amounts either retarded or inhibited growth. From the 



of hydrogen ion concentration, they are inclined to think that 

 the apparent resistance of the legume bacteria to alkali is due 

 to the slight concentration of hydroxyl ions in the mannitol 

 solution. This work confirms that of Salter. 



effect of acids and alkalis on soil 



b 



Gruzit ('17) studied the effect 



,cteria in soil solution, and found that soil bacteria were 



emelv sensitive to an acid 



H 2 S0 4 at a concentra- 



N 



N/1200 destroyed about 99.6 per cent of the bacteria; 

 killed about 93.0 per cent of the organisms; and N/2840 



ented the growth of about 



On the other 



hand, N/1000 alkali gave the maximum number of bacteria. 



Taylor ('17) determined the concentrations of a few organic 

 and inorganic acids necessary to check the growth of various 

 organisms. He obtained data which led him to conclude that 



ard 

 different ^ 



dity of the me 



Wolf and Harris 



observed 



dium may either delay or entirely stop the growth of B. perfring- 

 ens and B. sporogenes, the critical concentration of the former 

 being P H 4.82 



and 



4.94. All the acids tested 



similar effects and showed 



Wright ('17) studied the importance of uniform culture media, 

 and obtained data which clearly emphasize the many discrep- 

 ancies that exist when the culture medium is adjusted by means 

 of phenolphthalein titration. He found that the hydrogen ion 



