[Vor. 8 
318 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
ingacertain dependence upon the stimulating effects of hydrogen- 
ion concentration in such media. Maximum germination 
generally occurs between Py 2.5 and 4.0, but in the case of beet 
decoction the optimum zone extends from Pg 3.0 to 6.5. A 
secondary maximum near neutral is shown only in the case of 
"water HCl or KOH." The favorable range on the acid side 
extends more or less uniformly to Pa 2.0 in the solutions, but 
varies considerably in the alkaline solutions. The narrowest 
range of germination is exhibited in ‘‘water HCl or KOH," 
wo ] oL 74 ~ 
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Rreentage of Germination 
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Fig. 15. Penicillium cyclopium in Czapek’s full nutrient solution. 
extending to Pa 5.5, and followed in order by solutions of mannite, 
Pu 6.9, Czapek, Pu 7.9, peptone, Pu 8.7, beet decoction, Pa 9.8, 
and “water HCl or KOH,” Pu 10.0 +. The results obtained 
with these spores in solutions of mannite are very similar to 
those previously presented by the writer. It may be well to 
cite the concentrations of certain acids and alkalis allowing 
normal or almost normal development of the spores of Botrytis 
vulgaris in beet decoction, as determined by Clark (799): HCI, 
N/128; HNO,, N/256; H,SO,, N/64; acetic acid, N/256; mono- 
chloracetic acid, N/512; dichloracetic acid, N/256; trichloracetic 
acid, N/128; HCN, N/8192; KOH, N/64; and NH,OH, N/256. 
He concludes that the hydroxyl group, OH, is rather more 
toxic to the moulds studied than ionic H. 
