458 EXPERIMENT STATION RECORD. [Vol. 38 



forcing gas into tlie soil did not materially increase the rate at which it could 

 be introduced. Soil and water are both strong absorbents of hydrocyanic acid 

 gas. Retention of hydrocyanic acid gas by the soil is dependent upon the 

 character of the soil, while that of water remains constant under uniform 

 conditions of pressure and temperature. 



" The variability of gas absorption by the soil makes it practically impos- 

 sible in field work to estimate the dosage of .sodium cyanid required to give a 

 toxic effect on insects and at the same time to be within the margin of safety 

 to plants. In small amounts of soil of a uniform character it is possible to de- 

 termine experimentally the margin of- safety between certain insects and plants. 

 A heavy damp or a very wet sandy soil is almost impervious to hydrocyanic 

 acid gas. A pure sandy soil when wet will take up hydrocyanic acid gas only 

 in proportion to the amount of water present and this may again be given off, 

 but gas in contact with a clay soil either enters into a chemical combination 

 with some of the soil constituents or is adsorbed by the soil particles. 

 Gas generated in a .soil body diffuses with extreme slowness in clay soils or 

 very wet sandy soils, but in sand with a medium amoimt of moisture, the 

 diffusion of gas is much more rapid. The use of sodium cyanid offers a satis- 

 factory means of fumigating masses of loose, porous soil, especially those 

 with only small amounts of clay, or of seed beds and potting soil. Such treat- 

 ments allow of much wider range of concentrations when the soil is not occupied 

 by a. crop." 



Ventilation after fumigation. — Artificial ventilation of ships after fumi- 

 gation with hydrocyanic acid gas, S. B. Grubbs {Pub. Health Rpts. [U. S.], 

 82 {1911), No. 42, pp. 1151-1161, pis. 2). — "Quarantine stations at which hydro- 

 cyanic acid gas fumigation is practiced should be equipped with mechanical 

 means for artificial ventilation. The gasoline-driven fan as adapted for this 

 use is satisfactory for the prompt ventilation of compartments of vessels after 

 fumigation. For the expeditious handling of large vessels three machines are 

 recommended, two of the horizontal pattern (downward thrust) and one of the 

 vertical pattex-n (horizontal thru.st)." 



Fumigation hints {Cal. Citrogr., 2 {1911), No. 12, p. ^).— This is a summary 

 of recommendations made by R. S. Woglum of the U. S. Department of Agricul- 

 ture relative to the injury by and dosage of hydrocyanic acid gas in fumigation 

 work with citrus. Attention is called to the fact that trees, the branches of 

 which have been sprayed with Bordeaux mixture or painted with Bordeaux 

 paste, should not be fumigated since it will result in a serious burning. Trees 

 sprayed with lime-sulphur are unaffected by fumigation, as is the case with 

 trees of which the trunk alone has been treated with Bordeaux. 



Effect of smelter gases on insects, R. W. Doane {Science, n. ser., 46 {1911), 

 No. 1186. pp. 295, 296). — During the course of several summers spent in 

 studying insects in regions where smelters are located, the author has detected 

 no differences in the number of insects or the extent of insect injury due to the 

 presence of smelter gases. Fumigation tests with sulphur dioxid in strengths 

 of from 5 to 25 parts to 1.000,000 parts of air failed to demonstrate an insec- 

 ticidal effect, and he concludes that the sulphur dioxid given off by the smelters 

 has no effect whatever on the insects in that region. 



The natural immunity or resistance of plants to insect attack, R. C. 

 Treherne {Agr. Gas. Canada, 4 {1911), No. 10, pp. 855-859). — A general dis- 

 cussion of this subject. 



Some problems of sex ratios and parthenogenesis, 0. B. Williams {Jour. 

 Genetics, 6 {1911), No. 4, PP- 255-261, figs. 5). — "Aleyrodes vaporariorum has 

 two races, one of which, found in England, produces females parthenogenetic- 



