420 



ANNALS OF THE MISSOURI BOTANICAL GARDEN 



[Vol. 9 



vided sulphur yields a volatile product more readily. On the other 

 hand, the peculiar relation of this toxicity to a definite range of 

 hydrogen-ion concentration points rather towards the probability 

 that sulphur is toxic because of a compound produced that may 

 be volatile, the production of this compound being affected direct- 



by th 



does not seem probable that th 



sulphur particle as such could be rendered non-toxic by so slight 

 a change in reaction as has been shown to govern its fungicidal 

 property. 



To determine these points a series of experiments was arranged, 

 using flowers of sulphur, hydrophilic and hydrophobic * colloidal 

 sulphur. The organisms used were Botrytis cinerea, Colleto- 

 trichurn Gossypii, and Sclerotinia cinerea. 

 dure was the same as in the preceding experiments, with the fol 



The method of 



modifications: The spores were placed 



Irops of 



buffered solution without sulphur. The sulphur suspen- 

 re placed only at the bottom of the cells. In this way the 



direct contact with the sulphur, the distance 



between culture drop and cell liquid being the height of 

 which was 8 mm. The cultures were incubated 

 results are given in table ii. 



C. The 



TABLE II 



PERCENTAGE OF GERMINATION 



Organism 



Botrytis cinerea 



C olletotrichum 

 Gossypii 



Sclerotinia cinerea 



Form of Sulphur 



Without sulphur 



Flowers of sulphur 



Hydrophilic colloidal 

 sulphur 



Hydrophobic colloidal 

 sulphur 



Hydrogen-ion concentration (P H ) 



1.6 



2.43.2 



4 

 4 



3 



4 



Without sulphur 



Flowers of sulphur 



Hydrophilic colloidal 



sulphur 



Hydrophobic colloidal 

 sulphur 



Without sulphur 



Flowers of sulphur 



Hydrophilic colloidal 

 sulphur 



Hydrophobic colloidal 

 sulphur 

















 





 



76 

 74 



60 



71 





 











51 

 50 







36 



94 

 91 



58 



4.2 



24 

 22 



10 



26 



84 

 66 







19 



90 

 91 



12 



95 84 



38 

 37 







28 



5.4 



95 

 70 







8 



5.8 







86 

 84 



8 



53 

 51 







44 



82 

 74 







10 



76 



78 



54 



6.4 3.87.48.4 



56 

 51 



61 



90 74 



55 



50 



58 

 59 







21 43 47 



53 



70 

 65 



3 



61 





57 



58 



24 



65 59 



1 Precipitated sulphur. 



31 

 3 





50 



52 32 



46 

 45 







42 



9 

 11 



14 

 11 



10 



3 

 



2 



















