CONTENTS. 



Page. 



Reasons for the investigation 5 



Preliminary work at Washington, IX C 8 



Plan of the experiment 8 



Observations 9 



Summary of results 11 



Organization of cooperative work 11 



Preparation of samples 11 



Directions for spraying 12 



Report from the Maryland station 12 



Report from the New York station 16 



Report from the Rhode Island station 19 



Report from the South Carolina station 20 



Report from the New Hampshire station 23 



Report from the Oregon station 25 



Summary 30 



