304 FimglcUlal Properties of Certain Spray-fiuiih 



The two solutions, diluted in this way, exhibited very similar fungicidal 

 behaviour. 



In all the experiments just described the spray fluid contained 

 1 % of soft soap, added to ensure uniform spreading. In view of the 

 possibility that this addition of soap exercised some disturbing influence, 

 saponin was substituted for soap and a fresh comparison made between 

 Solutions VIII and XI. On refereiK^e to p. 297 it will be seen that 

 under these circumstances the fungicidal action of these two fluids 

 was similar when they contained equal amounts of polysulphide sulphur. 



These results seem to indicate a parallelism between the fungicidal 

 action and the polysulphide sulphur content of these solutions. It 

 seems that ammonium polysulphide solutions containing equal amounts 

 of polysulphide sulphur behave in exactly the same way fungicidally. 



From the foregoing results it was thought possible that ammonium 

 polysulphide solutions and hme-sulphur solutions, having the same 

 polysulphide content, would have the same fungicidal action. To ascer- 

 tain whether this were the case, a lime-sulphur solution, made in the 

 laboratory, and containing 17'02 % polysulphide sulphur, was diluted 

 until the polysulphide sulphur content was 0-078 % when it was 

 sprayed on mildewed leaves; the opposite and similarly mildewed leaves 

 at the same nodes being sprayed with an ammonium polysulphide 

 solution (XI), also containing 0-078 % of polysulphide sulphur. The 

 results given in Table 3 show how very similar these two solutions were 

 in their fungicidal action. In both these solutions saponin was used 

 instead of soap so as to secure a fair comparison. These two solutions 

 were again used at a different strength, each having a polysulphide 

 sulphur content of 0-113 %, and again similar action was observed. 



When the lime-sulphur solution previously referred to as having 

 been made in the laboratory was diluted so that it contained 0-23 % 

 of polysulphide sulphur it was found to be completely fungicidal. A com- 

 mercial sample containing 23-21 % of polysulphide sulphur was likewise 

 diluted until it also contained 0-23 % polysulphide sulphur, and this 

 also was found to be completely fungicidal. Thus when working with 

 lime-sulphur solutions as with ammonium sulphide solutions there 

 seems to be this dependence upon polysulpliides for fungicidal character. 

 With the object of gaining information as to whether the higher poly- 

 sulphides are more potent as fungicides than the lower polysulphides, 

 special efforts were directed to prepare stock solutions of different 

 chemical composition. For example, it was desired to make use of a 

 solution for spraying purposes containing mostly low ammonium 



