HORTICULTURAL RESEARCH 499 



such as carbon disulphide, chloroform, ether or benzene, produced 

 the same results as heating to a moderate temperature, the amount 

 of soluble matter in it being increased and the soil thereby 

 rendered slightly toxic to seeds. Such treatment was equivalent 

 in its effect to that produced by heating the soil to about yo° ; 

 and it was impossible to attribute this to any indirect action of 

 the antiseptic, through its modifying the bacterial growth in the 

 soil, for it was possible to complete the whole operation of treat- 

 ing the soil with the antiseptic, allowing this to evaporate and 

 obtaining an aqueous extract of the soil, within a period of from 

 20 to 60 minutes, during which time very little bacterial growth 

 could have occurred ; yet in this case the soluble organic matter 

 in the soil was found to have been increased by 61 per cent. 

 Moreover, after a soil has been treated with an antiseptic the 

 soluble matter in it decreases with the lapse of time : after 

 18 hours the original excess of 61 per cent, was reduced to about 

 35 per cent, and after five weeks to 16 per cent. : so that the 

 presence of the excess of soluble matter cannot be explained by 

 assuming it to be the product of the growth of bacteria : it is 

 evidently a direct product of the chemical action of the antiseptic 

 and it is, evidently also, a very unstable product. 



The conditions under which the toxic substance in heated 

 soils is decomposed was then investigated. It was found that 

 when the soil was kept excluded from air, even in a thoroughly 

 wet condition, it remained unaltered, giving, after several months, 

 the original values for the soluble matter present and for 

 its toxic action towards germinating seeds. But if freely 

 exposed to air and kept moistened, the amount of soluble matter 

 rapidly decreased and at the same time it lost (in three months) 

 its toxic properties nearly entirely. A similar but much 

 slower change occurred when the soil was kept in a fairly 

 dry condition. 



It is clear, therefore, that the toxic substance is of an easily 

 oxidisable nature and that it would soon be destroyed in any 

 ordinary cultural experiments, in which free exposure to air and 

 repeated watering have to be adopted. From the results obtained 

 with antiseptics, it further appears that the oxidation must 

 be very rapid at first, being considerably reduced even in a few 

 hours, though some of the toxin may persist, as shown by 

 the results with heated soil, after several months' exposure. 

 In spite, however, of the toxic effect having nearly disappeared 



