(54 PROCEEDINGS OP SECTION K. 



after ignition, e.g., strong hydrochloric acid (sp. gr. 1.1), citric 

 acid (1 per cent.) and nitric acid t-. The results are very- 

 irregular and vary in different directions, being frequently identical, 

 but point to the conclusion that in the case of heated soil, at all 

 events, the increased fertility is not due to the greater solubility 

 of the recognised plant-foods. Any considerable differences occur 

 only in cases where the quantities of plant-food are extremely 

 small, and are probably due to experimental errors. 



C. B. Lipman (New Jersey Agricultural Experiment Station, 

 Bull. 248) carried out experiments in which previously sterilized 

 soil was infected with filtered suspension so as to remove the pro- 

 tozoa. He finds no difference in results when such filtered liquids 

 are used, and when unfiltered suspensions, containing protozoa, are 

 employed, and is " unable to confirm the claims of Russell and 

 Hutchinson as to the influence of protozoa in modifying the amount 

 of work done by decay bacteria." 



Another view of the action of heat upon soils has been more 

 recently advanced by O. Schreiner and E. C. Lathrop (J our- 

 i\al American Chemical Society, Vol. 34, p. 1242), and 

 E. C. Lathrop (ibid., p. 1260). These authors find that 

 heating the soil results in an increase in the water 

 soluble constituents and in acidity, although ammonia and amines 

 are formed. Heating the soil produces simultaneously both 

 beneficial and harmful organic compounds. Amongst the benefi- 

 cial are xanthine and hypoxanthine, guanine, cytosine and argi- 

 nine, and among the harmful hydroxystearic acid. These sub- 

 stances, if already present in the soil, are increased by heat, and 

 if not originally present are produced by the action of heat. The 

 heated soil possesses at first a decreased fertility, owing to the pro- 

 duction or increase of dihydroxystearic acid, but when this in- 

 gredient disappears either through oxidation, cropping, addition of 

 lime or nitrate, the fertility of the soil is increased. This explana- 

 tion, it will be seen, opposes the conclusions of Russell and 

 Hutchinson as far as the effect of heating is concerned, and at- 

 tributes it to the alteration of the proteid matter of the humus 

 rather than to the action of micro-organisms. 



There are thus several theories advanced to account for the 

 action of heat and of antiseptics upon the soil. On the one hand, 

 it is attributed in both' cases to a partial sterilization of the soil as 

 a result of which certain organisms are destroyed which are hostile 

 to the ammonia-producing bacteria ; on the other hand, the action 

 of antiseptics may, it is suggested, be due to the removal of an 

 impervious wax-like material surrounding the soil grains, the pre- 

 sence of which hinders their being attacked by soil-solvents, and, in 



