222 FUMIGATION METHODS 
The following letters or quotations from scientific 
and practical men who have either used hydrocyanic 
acid gas or are thoroughly familiar with its properties 
and economic values are interesting in this conne¢tion. 
We have alluded to the early history of the discovery 
FIG. 82—FUMIGATED CITRUS 
Orchard of J. W. Henderson, near National City, California, only a 
short distance from the Stearns ranch, on which Fig. 83 was 
taken. Orchards about the same time. Note the difference. 
of the gas as an insecticide in Chapter I. There seems 
to be some misunderstanding as to its first application 
to nursery stock. In the ‘‘ Year-Book of the United 
States Department of Agriculture for 1899,”’ Dr. L. O. 
Howard, Entomologist, is of the opinion that he first 
recommended the use of hydrocyanic acid gas as a dis- 
