1922] 



YOUNG — THE TOXIC PROPERTY OF SULPHUR 



423 



TABLE IV 



PERCENTAGE OF GERMINATION 

 COLLETOTRICHUM GOSSYPII 





Hydrophobic colloidal sulphur 



Flowers of sulphur 



Ph 













-0 2 



| +o 2 



-o 2 



1 +o 2 



2.4 



















3.2 



26 



18 



22 



18 



4.2 



42 



2 



51 



16 



5.4 



56 



13 



60 



10 



5.8 



60 



37 



68 



43 



6.4 



66 



62 



54 



56 



EXPERIMENT 7. THE INFLUENCE OF H 2 ON THE TOXICITY 



OF SULPHUR 



The influence of water on this volatile compound was next 

 studied. Dry colloidal sulphur was prepared by centrifuging hy- 

 drophobic colloidal sulphur and the residue dried at room tem- 

 perature. This was placed in the bottom of Van Tieghem cells. 

 Spores of Sclerotinia cinerea were placed in sterile distilled water 

 on sterile cover slips and inverted over the cell. The cell was not 

 made air-tight, thereby not eliminating any other factor except 



water. Checks were arranged in which a suspension was used in- 

 stead of the dry sulphur, other conditions being the same. All the 

 cultures were placed in a moist chamber at room temperature. 

 There resulted from this experiment no inhibition when dry sul- 

 phur was used, while the suspension gave the same amount of in- 

 hibition as reported in table hi. Oxygen and water are necessary 

 factors in the formation of the toxic volatile compound of sulphur. 



Chemistry of Hydrophilic Colloidal Sulphur 



The results of all the foregoing experiments point towards 

 hydrophilic colloidal sulphur as containing the toxic substance 

 produced by the oxidation of the ordinary forms of sublimed 

 and precipitated sulphur. It is as toxic in closed-ring cells 

 where little oxygen is available as in open aerated cells. The 

 other forms of sulphur tried are toxic only when oxygen is pres- 

 ent. Hydrophilic colloidal sulphur is toxic at 21-22° C. to 

 Botrytis cinerea, Macrosporium sarcinaej orme , Gloeosporium 

 venetum, and Colletotrichum Gossypii, all of which are very re- 



