LETTER OF TRANSMITTAL. 



United States Department of Agriculture, 



Bureau of Entomology, 

 Washington, D. C, September 11, 1912. 

 Sir: I have the honor to transmit herewith, for publication as 

 Bulletin No. 90 of this bureau, three papers comprising a report on 

 an investigation of hydrocyanic-acid gas fumigation of citrus orchards 

 in southern California. The preliminary report on the subject was 

 published as Bulletin No. 79 of this bureau under the title "Fumi- 

 gation Investigations in California." The present final report is 

 divided into three parts, which were published separately on May 10 

 and 13, 1911: I, entitled "Fumigation of Citrus Trees/' by R. S. 

 Woglum, a special field agent of this bureau, containing the main 

 report on the field investigations and discussing the various details 

 of fumigation procedure; II, a paper by Mr. Woglum, "The Value of 

 Sodium C} 7r anid for Fumigation Purposes"; and, III, one by Mr. C. C. 

 McDonnell, Chief of the Insecticide and Fungicide Laboratory, 

 Bureau of Chemistry, "Chemistry of Fumigation with Hydrocyanic- 

 acid Gas." 



Respectfully, L. O. Howard, 



Entomologist and Chief of Bureau. 

 Hon. James Wilson, 



Secretary of Agriculture. 



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