l82 



BOTANICAL GAZETTE 



[march 



In about 200 preliminary cultures it was found that the addition of 

 small quantities of acids such as HCl, HNO„ and H.SO^ had a 

 stimulating effect on the growth of Penicillium. This is only an 

 instance of the general rule that poisonous substances act as stimu- 

 lants when given in sufficiently dilute concentration. These two 

 series were carried through with great care and uniformity, in order 

 to get, if possible, a more accurate quantitative statement of the facts 



preliminary 



There is considerable individual 



difference in the cultures, as is noted by reading the figures in 



nm, the five cultures be 



smi 



stimulation of stow 



? another. Neverthe- 

 The addition of min- 

 ;h. The nitric acid 

 hvdrochloric. The 



m each case gave a greater stimulation than the hydrochloric, 

 sulfuric acid m one case (table II) gave a greater increase than hydro- 

 chloric, while in the other case [table III) its effect was about equal 

 to that of the HCl. These observations agree with those made on the 

 preliminary cultures. Many of the cultures seemed to show that 



chloric 



greater stimulation 

 as thought possible that HCl might be 



poison at the concentration used, but a series of cultures {table IV] 

 ved that the optimum for stimulation was much higher than 0.004W 



cannot 



actually a milder stimulant than HNO3, 



H,SO^. In addition to the usual mineral 



which HCl was added. 



KCl per 100" of cultur 

 ion, CI, in the cultures tc 

 I cultures produced spores 



Each flask received o _ finsnn 



TABLE TV 



concentration o . 3 GM. per liter. . 



CONCZSTHATION OF ACID 



Numbo- 



*.*■• 





0.002» , O.O04» 



r 



i 



4 



o.oG6n 



6 



B 



o.oo8» ] o.oi2» ; o.GiCn , o.oa4» 



r. 



3 

 4 



3 



I 



Che<^ 



208 



209 

 209 

 214 



t 



172 



227 



232 



239 



242 



146 



185 



266 I 



280 ' 



266 

 268 



284 



29s 



\ 



183 



255 



2S7 

 260 



273 





193 , 



239 

 246 



255 



255 



236 j 



239 

 240 



246 

 257 



163 

 171 



173 

 181 



181 



3-6 



