14 THE FERTILITY OF THE SOIL 



heating effective, but antiseptics like chloroform, carbon 

 disulphide vapour, give rise to a similar result. For 

 example, you will remember how the vineyards of 

 Europe were devastated some thirty years ago by the 

 attacks of Phylloxera, and though in a general way the 

 disease has been conquered by the introduction of a 

 hardy American vine stock which resists the attack 

 of the insect, in many of the finest vineyards the 

 owners have feared to risk any possible change in 

 the quality of the grape through the introduction 

 of the new stock, and have resorted instead to 

 a system of killing the parasite by injecting carbon 

 bisulphide in the soil. An Alsatian vine-grower who 

 had treated his vineyards by this method observed that 

 an increase of crop followed the treatment even in cases 

 where no attack of phylloxera occurred. Other obser- 

 vations of a similar character were reported, and within 

 the last five years the subject has received some con- 

 siderable attention until the facts are now definitely 

 established. Here are some illustrations of the sort 

 of results which may be expected. The crop becomes 

 approximately doubled, if the soil has first been heated 

 to a temperature of 70 to 100 degrees for two hours, 

 while treatment for 48 hours with the vapour of toluene 

 or chloroform, followed by a complete volatilization of 

 the antiseptic, brings about an increase of about 30 per 

 cent. Moreover, when the material so grown is analysed, 

 the plants are found to have taken very much larger 

 quantities of -nitrogen and other plant foods from the 

 treated soil, hence the increase of growth must be due 

 to larger nutriment and not to mere stimulus. The 

 explanation, however, remained in doubt until it was 

 recently cleared up by Drs. RUSSELL and HUTCHINSON, 



