IV 



Contents 



No. 4 (April, 1917) 



1. Accessory Wetting Substances with Special Reference to 



Paraffin Emulsions. By A. H. Lees, M.A. ... 141 



2. Empusa Muscae versus Musca domestica L. By H. T. Gussow. 



(With Plate XXI.) 150 



3. A Blossom Wilt and Canker of Apple Trees. By H. Wormald, 



M.Sc. (Lond.), A.R.C.Sc. (With Plates XXII— XXIV.) . 159 



