VI HYDROCYAXIC-ACID GAS FUMIGATION IN CALIFORNIA. 
All information, as acquired, of direct bearing on the fumigation 
practice has been given freely to the public as soon as its economic 
value was established, largely by means of addresses, demonstrations, 
and printed reports. 
In the present bulletin an attempt has been made to present a * 
succinct account of the completed results of this fumigation investi- 
gation as well as a brief treatment of the salient features of fumi- 
gation as practiced in California at the present time. It is of the 
nature of a handbook on the most up-to-date equipment, methods, 
and directions in orchard fumigation. Full advantage has been 
taken of the results of other investigators in fumigation; yet in such 
cases due credit is given to the proper source. The information 
given in Bulletin 79 of this bureau, which is a preliminary report on 
this investigation, has been largely included in the present bulletin 
in summarized form. 
The writer desires to acknowledge his indebtedness to the man}' 
people who have assisted him during this investigation and facilitated 
the progress which has been made. To. Mr. C. L. Marlatt, Assistant 
Chief of the Bureau of Entomology, he is especially indebted for 
valuable assistance and advice. Acknowledgment is also due to 
Mr. Frederick Maskew, who most capably assisted him in the per- 
formance of man}" of his experiments during the period from Decem- 
ber, 1907, to August, 1909. Valuable assistance was rendered by 
Mr. E. K. Sasscer during the months of August, September, and 
October, 1909. Mr. TV TV Yothers was engaged in the work during 
November, 1909. To the Hon. J. TV. Jeffrey, State commissioner of 
horticulture of California, credit is due not only for his activity in 
paving the way for this investigation, but also for the able support 
given by him since field work was commenced. To Mr. William Wood, 
of Whittier, Cal., the writer acknowledges his indebtedness for 
assistance in introducing the improved system of fumigation in the 
region adjacent to Whittier, as well as for practical advice with regard 
to citrus insects and their control, a subject about which Mr. Wood 
is especially well informed. This occasion is also taken to thank the 
various horticultural officers of southern California, packing-house 
managers, and the many citrus growers who have assisted and sup- 
ported this investigation. 
The cooperation of the Bureau of Chemistry of the United States 
Department of Agriculture has been an important adjunct of this 
investigation, and to Mr. J. K. Haywood, Chief of the Miscellaneous 
Division of that bureau, and Ins assistants the writer is indebted for 
the carrying out of all the chemical analyses and laboratory tests of 
materials and products necessary to the working out of the field 
experiments. 
R. S. W. 
