252 SCIENCE AND FRUIT GROWING 



of the excess of organic matter rendered soluble by the heating. 

 Twelve different" soils were examined, and they all behaved in a 

 similar manner on heating, though the amount of organic matter 

 rendered soluble by the heating was not an invariable guide as to 

 the extent to which germination was affected. Similarly, though 

 germination generally occurred less readily in those unheated 

 soils which contained a smaller amount of total soluble matter, 

 this was not invariably the case, as would follow from the 

 soluble matter differing in different cases. Whether any of the 

 soluble constituents of soils is actually favourable to germina- 

 tion, or not, appeared doubtful ; certainly, in general, they are 

 the reverse, and germination was found, in such cases as were 

 examined, to take place more readily in an inert medium (e. g. 

 wet sand) than in earth ; this affording further evidence that a 

 substance having a toxic effect on germination is present in 

 some soils even under ordinary conditions (see p. 250). 



That bacterial conditions do not play any part in these results 

 on the germination of seeds is evident from the results of the 

 experiments themselves : thus, the bacterial changes consequent 

 on heating soils result, after some lapse of time, in a large 

 increase in the bacterial contents, provided the temperature to 

 which the soil has been heated has reached 60 to 100; but 

 it leads to an extinction of bacterial life if it has been as high 

 as 125. The germination values, on the other hand, show a 

 continuously progressing effect from the lowest to the highest 

 temperature of heating, 150. Added to this, it was found that 

 seeds will germinate in a sterile medium ; that sterilised and un- 

 sterilised seeds germinate with equal readiness, and that sand, 

 even when thoroughly inoculated with soil bacteria, behaves in 

 the same way towards germination, whether it has, subsequently 

 to the inoculation, been heated or not. 



Against this view, however, it may be urged that the treat- 

 ment of soil with antiseptics produces the same effect as that 

 of heating it, and that with antiseptics, such as benzene, ether, 

 chloroform, carbon disulphide, etc., there can be no chemical 

 action on the substances in soil, and that their action must, 

 therefore, be confined to the organisms in the soil. But this 

 contention seems untenable ; for the only way in which such 

 substances can act on organisms, either as antiseptics or as 

 anaesthetics, is by affecting the chemical processes on which life 

 depends : this implies chemical activity. Moreover, these anti- 

 septics undoubtedly act on organic substances in the absence 

 of living organisms, and act on them very rapidly; this was 



