' 

LE 
Treatment consists in inclosing a tree (or nursery stock in greater 
or less quantities at once) with a tent and filling the latter with the 
poisonous fumes generated with potassium cyanide and sulphuric acid. 
The present practice of “gassing” or “‘fumigating,” as it is called, 
differs very little from the method employed a number of years ago 
when the process was first perfected, the main difference being in the 
fact that refined cyanide (98 per cent) is generally used in preference to 
the fused 58 per cent grade hitherto employed. The latter gives good 
results when it is uniform, but, unfortunately, this is rarely the case, 
and even in different parts of the same barrel great variation often 
occurs. Only about two-thirds as much of the stronger cyanide is used 
Se, 
SSS 
S 













































Fic. 1.—Tenting trees for gas treatment, San Diego, Cal. (author's illustration). 
as of the weaker grade. The following table, prepared by Mr. John 
Scott, horticultural commissioner of Los Angeles County, gives the 
proportion with the stronger cyanide for trees of different sizes: 













: : d Diameter | r la ae ee Cyanide 
ee aka aa fe | (fiuid aundeey: (quid ae a gesieea)e 
| 6 4 1 4 4 
8 6 24 14 14 
10 8 34 | 2 2 
12 10 6 3 3 
12 14 9 44 44 
14 14 10 5 5 
16 16 12 5k 54 
18 16 12 6 6 
20 16 13 64 6} 
22 18 15 | 74 7 : 
24 20 16 8 8 
26 20 164 Bt 84 
30 20 | 174 8k 8h 
| 
1722—No, 19——2 


