1919] 



WEBB — SPORE GERMINATION AND H ION CONCENTRATION 1 16 



minimum germination is obtained. At P H 7.4 there is a slight 

 increase followed by a gradual decline to the culture possessing an 

 exponent 9.6, the limiting concentration appearing to be beyond 

 10.0+ . With increase of hydrogen ion concentration above P H 

 4.4. there is a decrease in percentage of germination, but the 



evidently lies above 



H 



2.8. Readings at incubation periods of 27 and 37 hours, re- 

 spectively, give very similar results to those of the first reading, 

 the only difference being that relatively slight germination is 

 obtained in the culture with the value P H 10.0+, which was 



In no other case did 



Penicillium germinate at this relatively extreme alkalinity, and, 



formerly the limiting concentration. 



inasmuch as these spores frequently collected in bunches 



the apparently erratic germination might be due 



this 



At 27° C. maximum germination is obtained in the culture 

 where the exponent is P H 3.1, and the curve proceeds in the same 

 general direction as before with the exception that minimum 

 germination is obtained at P H 6.2, as compared with P H 7.0 in the 

 former case. A slight rise is evident at P H 7.0, only to be followed 

 by a decline at P H 7.4. On the acid side, the limiting concentra- 

 tion occurs below P H 2.8, whereas on the alkaline side it occurs 



about P H 8.8. Both examinations of prolonged incubation sub- 

 stantiate the data obtained from the first reading, the only dif- 

 ference being a gradual increase of germination with increase of 



incubation interval. 



The same curve of germination is obtained at 31° C. The 

 characteristic maximum occurs in the same culture as before, 

 exhibiting the value P H 3.1; germination decreases with de- 

 crease in hydrogen ion concentration to the culture testing F 

 7.0 where the minimum is obtained. A slight stimulation in 

 germination is noted at P H 7.4, but no germination whatever is 

 noticed with further decrease in hydrogen ion concentration. 

 With an additional incubation of nine hours at the same tempera- 

 ture, germination relations remain practically the same. The 

 range of germination is extended to P H 8.8, as compared with ] 

 7.4 at the first examination, and germination is extremely low i 

 P H 7.0. Mycelial growth was so luxuriant in this series that it wj 



