290 Fungicidal Properties of Certain Spray-fluids 



2 % of Solution No. IX and 1 % soft soap was used, this was prepared 

 by diluting H c.c. of stock solution to 200 c.c. with distilled water and 

 then adding 200 c.c. of a 2 % solution of soft soap in distilled water. 



Details of Biological Ob.servations. 



Anrnmnivm polysulphide Solution I. 



This stock solution diluted 1 : 50 and upwards is not fungicidal, 

 although at 1 : 50 it is nearly fungicidal, killing some patches and severely 

 checking the others. 



As with our experiments in 1915, it was found that the solution 

 diluted 1 : 20 and containing 0-5 % or 1 % soft soap, is fungicidal for 

 the "powdery" conidial stage. At this strength it did not kill the 

 young non-powdery stage of the mildew in two experiments, but in a 

 tliiid experiment, where the host plant was H. Lnpiilus var. conlifolins, 

 the effect was fungicidal and very striking. 



The solution, diluted 1 : 20, was found to lose much of its potency 

 if allowed to stand, after dilution, for four days, and had no fungicidal 

 value after six days. 



Ammonium polysulphide Solution 1 1 (with 1 % soap). 



Although in two experiments this solution diluted 1 : 1 60 killed the 

 patches of mildew, there is reason to believe that this happens only 

 when the patches are on old leaves and therefore with a comparatively 

 slight power of resistance. In three later experiments (with 14 leaves), 

 where a record exists as to the comparative age of the sprayed leaves, 

 it was found that the solution at this strength has no fungicidal power 

 over the powdery conidial stage on the younger leaves. The solution 

 at 1 : 100 has considerable fungicidal power, but in no case did it kill 

 all the patches on all the leaves sprayed in the experiment. At 1 : 50 it 

 was fungicidal for the powdery conidial stage in two out of four experi- 

 ments. At 1: 30 it was fungicidal in two experiments (with 12 leaves). 

 At this strength the solution may injure the leaves. 



In some of the experiments it became obvious that the death-point 

 of the "powdery" mildew-patch varied according to the age of the leaf 

 on which it resided. Thus in Experiment 31, with the solution at 1 : IGO, 

 two leaves were sprayed on one plant; the "upper" leaf bore eight 

 powdery patches, and the "lower" many powdery patches. On the 

 fifth day after spraying, the patches on the lower leaf were "much 

 checked or even semi-obliterated," while on the upper leaf all the 



