550 EXPERIMENT STATION RECORD. [Vol.41 



used in Bordeaux mixture, lime-sulphur solution, or with an excess of lime 

 in the spray. 



The adulteration of insect powder with powdered daisy flowers (Chrsyan- 

 themum leucanthemum), R. C. Roark and G. L. Keenan ( U. S. Dept. Agr. 

 Bui. 795 {1919), pp. 12, pis. 2, fig. 1). — The authors' studies are reported under 

 the headings of adulteration of insect powder and uses, insecticidal action, 

 chemistry, and morphology of the ox-eye or field daisy (C. leucanthemum) . 



It was found that while there are certain differences in the chemical com- 

 position of C. cmerari(£folium and C. leucanthemum a chemical analysis is 

 insufficient to show adulteration of insect powder with daisy flowers. Adultera- 

 tion of insect powder with powdered daisy flowers can be definitely determined 

 by microscopic examination, the powdered daisy flowers being distinguished 

 by (a) the irregular dark-red fragments of the acliene, and (b) the palisade- 

 like cells comprising the costal tissue of the achene. 



A Ust of 40 references to the literature cited is appended. 



Fumigation with liquid hydrocyanic acid, H. J. Quayle {California Sta. 

 Bui. 308 {1919), pp. 393-407, figs. .J).— This is a summary of information on the 

 present status of fumigation with liquid liydrocyanic acid, first used largely 

 in experimental tests on citrus trees in California in 1916 and on an extensive 

 commercial basis in 1917. In addition to the scale insects of citrus trees, more 

 than 75,000 ladybird beetles liave been used in comparative tests as an index 

 of results. The results have given discriminating data concerning the diffusion 

 of gas under the tent, showing that the place of greatest concentration is prac- 

 tically the reverse of that from the pot or portable generator. 



"The greatest possible yield is 108 lbs. or 18.56 gal. of anhydrous liquid 

 hydrocyanic acid from 200 lbs. of sodium cyanid (51 to 52 per cent cyanogen). 

 The amount of liquid hydrocyanic acid (95 to 98 per cent) that has been 

 recovered at the plant during the past year has been about 78 per cent of the 

 total available. The amount of gas evolved by the pot or portable generator 

 is estimated at 90 per cent of the total available gas. During the past year 

 75 per cent of the gas from a given amount of cyanid in the liquid form was 

 made to cover the same ground as 90 per cent from the same amount by the 

 ordinary methods of generation. Thus, while there has been a discrepancy 

 of 10 or 15 per cent in the actual amount of gas used through the liquid 

 method, the results in the field have not indicated any important difference on 

 the scale insects. Our own tests, however, both in the field and laboratory, 

 have indicated about such difference as would be expected. This apparent 

 discrepancy between our own tests and commercial work in the field may be 

 accounted for through the great variability in field work and by the difference, 

 as has been determined, in the diffusion of the gas from the different methods. 



" Field examinations are usually limited to an examination of the scales 

 within 6 or 8 ft. of the ground. Our own tests have included the top of the 

 tree as well. From these tests, when the results at the center and the bottom 

 only were considered, there was practically no diffei'ence between the liquid 

 and the pot, which harmonizes with the results in the field. When the results 

 at the center and top only were considered, the pot method was more efficient 

 than the liquid method. When the results in all parts of the tree are considered, 

 it is necessary to use about 20 ec. of liquid hydrocyanic acid (96 or 98 per 

 cent) to equal 1 oz. of sodium cyanid as given in the schedules of dosage now 

 in practical use. Units representing 20 cc. may therefore be submitted for 

 the ounces, and the atomizing machines should be graduated to deliver 20 cc. 

 from each ounce called for in the schedules." 



An account relating to this subject by Woglum has been previously noted 

 (E. S. R., 41, p. 164). 



