[Vol. 9 



432 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



A strong stream of water from the hose did not remove the sul- 

 phur from panes of glass. The method is being perf acted for 

 open-air use. 



Conclusions 



1. Flowers of sulphur is not sufficiently toxic to inhibit the 



germination of spores of Botrytis cinerea, Colletotrichum Gos- 



sypii, Macrosporium sarcinaeforme, and Gloeosporium Venetian 



in closed-ring cells at ordinary temperatures. Spores cf Sclero- 



tinia cinerea and Phomopsis Sojae were inhibited from germin- 

 ation. 



2. Finely ground flowers of sulphur was more toxic than the 

 unground flowers under the same conditions but only at a hy- 

 drogen-ion concentration of P H 4.0-5.5. 



3. Methods for the preparation of hydrophilic and hycrophobic 

 colloidal sulphur have been devised. 



4. Hydrophilic colloidal sulphur was extremely toxic :o all the 

 organisms used. 



5. Hydrophobic colloidal sulphur was slightly more toxic than 

 the finely ground flowers of sulphur. 



6. The chemical and fungicidal properties of lime sulphur were 

 studied. Before application lime sulphur contains 80.7 per cent 

 sulphur as calcium sulphides, 19 per cent as calcium thiosulphate, 

 and .03 per cent as sulphites and sulphates. After exposure to 

 the air for a few hours as a spray the sulphides disappear and 

 increasing amounts of sulphur are formed. The lasting effec- 

 tiveness of the mixture is due to the precipitated sulphur which 

 is about as toxic as hydrophobic colloidal sulphur. 



7. The toxic property of sulphur is not due to S0 2 , SC 8 or H 2 S, 

 or any of the common acids or oxides of sulphur, or to the sulphur 

 particle. Germ tubes grew normally in a heavy suspensic n of pre- 

 cipitated sulphur in closed-ring cells. 



8. The toxic property of sulphur is only exhibited when oxygen 

 and water are present. 



9. By chemical analysis the toxic property of sulphur has been 

 found to be pentathionic acid which is an oxidation compound 

 formed from sulphur and water. 



10. Pentathionic acid is volatile and is an active adsorption 

 compound. It is destroyed in acid and alkaline solutions. 



