478 FKiujiiidal l'rop< rti( s of (.'(/(a in SprKii-FiiiliU 



"controls" in the details of the experiments recorded below. The 

 spra3'ed leaves were regularly observed at intervals of a few days 

 from the first day after spraying until the action of the solution was 

 <letermined. Owing to the superKcialitv of tlte mildew, and the ease 

 with which the plants could be handled, no dilliculty was experienced 

 in accurately determining the biological condition of the fungus. 



In preliminary trials it was found that when patches of mildew 

 in an actively growing "powdery" condition are sprayed with aijueous 

 solutions, the spray (even when very finely divided and applied with 

 force) collects in minute drops on the surface of the densely packed 

 conidiophores and conidia, being prevented by the presence of air at 

 these places from uniformly wetting the fungus^. When, however, a 

 0-5 % or 1 % solution of soft soaj) is added, the wetting power of the 

 solution used is increased to such an extent that it spreads evenly and 

 uniforndy through all " powdery" patches'. In the case of lime-sulphur, 

 to which soap cannot be added for chemical reasons, 0-125 % or 0-25 % 

 of saponin^ was added, so as to secure, as far as possible, uniformity 

 in the spreading properties of the sprays used. 



Materials Used. 



For the sake of clearness, when considering tlie effect produced by 

 the various spraying fluids used, a brief description of the materials 

 comjjrising them is desirable. It should be mentioned in the first place 

 that for the purpose of decreasing the surface tension of the spray-fluids 

 and thus increasing their power of ivetting powdery surfaces, definite 

 quantities of soap have been used in the preparation of most of the 

 solutions employed. In other cases, where for chemical reasons soap 

 could not be used, as in the case of lime-sulphur, its place in the mixture 

 has been taken by saponin*. 



Soap. In all cases where soap has been used alone or in conjunction 

 with other substances the soap used was that known conuneirially 



' Mr S. U. Pickering has already called attention to this fact (lU/i Report Wnburn 

 Exper. Fruit Farm, p. 119 (1910)). 



- In sonic spraying experiments with certain washes <^ari'ied out inulcr practical 

 conditions in the open, Messrs Barker and Lees {Report Agric. and Hort. Research Station, 

 Long Ashlon, for 191i, p. 73) found that 2 "j^ soft soap solution did not thoroughly wet 

 the mildew, while a 2 °j^ paraffin emulsion did so. 



' Mr Pickering (loc. oil. p. 1.59) has pointed out that the action ol saponin resembles 

 that of soap in increasing the wetting properties of spray-fluids. 



* Vide \lth Keporl Woburn Exper. Fruit Farm. p. 159 (1910). 



