62 Eighteenth Report State Entomologist of Minnesota — 1920 



these leaves. Applying the same principles, it was found that sub- 

 stances somewhat similar to the cellulose, such as casein, gelatin, flour, 

 starch, saponin, and even leaf extracts or infusions gave good spread- 

 ing. Sprays of this type did not spread on waxy leaves unless driven 

 with such force that the spray was brought into contact with the 

 cellulose epidermis beneath the bloom. 



