1919] 



WEBB — SPORE GERMINATION AND H ION CONCENTRATION 221 



tion being obtained with the following concentrations, inclusive : 

 Aspergillus niger, P H 2.8-8.8; Penicillium cyclopium, 2.8-10.0+ ; 

 Botrytis cinerea, 2.8-7.0; Fusarium sp., 2.8-10.0+ ; and Lenzites 

 saepiaria, 2.8-7.0. 



(3) It is not until a hydrogen ion concentration of P H 2.8 or 

 above is reached that inhibition of germination of the forms 

 studied is noticed. 



(4) Aspergillus niger, Penicillium cyclopium, Botrytis cinerea, 

 and Lenzites saepiaria show a maximum of germination in the 

 medium employed at P H 2.8-3.1 ; Fusarium sp. exhibits a second- 

 ary maximum at this concentration. 



(5) Fusarium sp. gives a pronounced maximum of germina- 

 tion at P H 7.4, and Penicillium cyclopium exhibits a minor second- 

 ary maximum at P H 7.0-7.4. 



(6) For equal removes from the neutral point, OH ions 

 appear to be relatively more toxic to the spores studied than 

 H ions. 



(7) With increase in length of intervals of incubation, the 

 relations of germination to hydrogen ion concentration remain 

 practically the same. 



(8) The curves of germination for any organism are practically 

 identical, whether incubated at 22° C, 27° C, or 31° C. 



The writer takes pleasure in acknowledging his indebtedness 

 and extending his. sincere thanks to Dr. B. M. Duggar for sug- 

 gesting and directing the problem and for kindly criticism and 

 advice; and to Dr. George T. Moore for the privileges and 

 facilities of the Missouri Botanical Garden. 



Graduate Laboratory, Missouri Botanical Garden. 



Bibliography 



Ayers, S. H. ('16). Hydrogen ion concentrations in cultures of streptococci. [Jour. 

 Bact. i : 84-85. 1916.] 



Brooks, C. ('06). Temperature and toxic action. Bot. Gaz. 42: 359-375. 1906. 



Clark, J. F. ('99). On the toxic effect of deleterious agents on the germination and 

 development of certain filamentous fungi. Ibid. 28: 289-327, 378-404. 1899. 



Clark, W. M., and Lubs, H. A. ('17). The colorimetric determination of hydrogen 

 ion concentration and its application in bacteriology. Jour. Bact. 2: 1-34, 

 109-136, 191-236. /. 1-8. 1917. 



