92 PLANT PRODUCTS 



contain about 30 to 50 per cent, of crude naphthalene. These 

 mixtures are rather drier, and more convenient to handle. 



Soot may be considered to have a value partly dependent 

 on tar and other poisonous materials. 



There is considerable reason for supposing that many of 

 these poisonous substances do some slight injury to the crop, 

 but if the destruction of wire worms, etc., is on a sufficiently 

 large scale, the subsequent benefit will more than compensate 

 for the temporary injury. It is desirable that all these 

 substances should be applied to the soil at a considerable 

 interval of time before sowing seeds. If that is not practic- 

 able some slight good may perhaps be done by applying such 

 germicides between the drills, so as to keep as far away from 

 the plant as possible, but this latter practice must be 

 considered as open to some objections. Injudicious use of 

 soil fumigants has done much harm. 



REFERENCES TO SECTION II 



Russell, " Chalking : A Useful Improvement for Clays overlying the 

 Chalk," Journ. Board of Agriculture, 1916-17, p. 625. 



Hutchinson and Maclennan, " Studies on the Lime Requirements of 

 Certain Soils," Journ. Agric. Science, vii., p. 75. 



Collins, " Scheibler's Apparatus for the Determination of Carbonic 

 Acid in Carbonates," Journ. Soc. Chem. Ind., 1906, p. 518. 



Roscoe and Schorlemmer, vol. ii., p. 290. 



Lemstrom, " Electricity in Agriculture and Horticulture." 



Jorgensen and Priestley, " The Distribution of the Overhead Electrical 

 Discharge employed in Recent Agricultural Experiments," Journ. Agric. 

 Science, vi., p. 337. 



Blackman and Jorgensen, " The Overhead Electric Discharge and Crop 

 Production," Journ. Board of Agriculture, 1917-18, p. 45. 



Russell and Petherbridge, "Investigations on 'Sickness' in Soil," 

 Journ. Agric. Science, October, 1913. Russell, "Partial Sterilization of 

 Soil for Glasshouse Work," Journ. Board of Agriculture, 1911-12, p. 809; 

 1912-13, p. 809; 1914-15, p. 97. 



Russell and Hutchinson, " The Effect of Partial Sterilization of Soil on 

 the Production of Plant Food," Journ. Agric. Science, October, 1909. 



Buddin, " Partial Sterilization of Soil by Volatile and Non- Volatile 

 Antiseptics," Journ. Agric. Science, vi., p. 417. 



Russell, " Soil Conditions," p. 114. (Longmans, Green.) 



Wentworth, "Effect of Electricity on Sheep Raising," Journ. Board 

 of Agriculture, 1911-12, p. 519. 



Brenchley, " Inorganic Plant Poisons." (Camb. Univ. Press.) 



Hanley, "Lime and the Liming of Soils," Journ. Soc. Chem. Ind., 

 1918, p. 185 T. 



