134 HATCH EXPERIMENT STATION. [Jan. 



however, there is a gain or acceleration due to treatment, 

 the maximum acceleration being shown by the boiled loam. 



A comparison of the different strengths of solutions shows 

 that the one-eighth dilution produced the best results of any 

 of the treatments, that for boiled loam being the highest. 

 This series of experiments shows that decoctions of soils 

 variously treated induce acceleration in seed germination, 

 and that a laroer number of seeds o-erminated in decoctions 

 than in tap water. This increase is quite marked in dilute 

 decoctions (one-eighth strength), and Avould probably be 

 increased to some extent if the dilution should be carried 

 still further. In these experiments we have a chemical ex- 

 planation for the cause underlying acceleration and increased 

 germinating capacity in sterilized soils. Undoubtedly driv- 

 ing out the gases and the subsequent absorption and renewal 

 of fresh oxygen in sterilizing practices acts beneficially to 

 soil and induces the seeds to germinate more quickly, as 

 is shown by the aerating experiments previously reported. 

 By the process of aeration, or by soaking seeds in dilute 

 decoctions, many seeds germinate that otherwise would not; 

 but there is no ground for belief that any of these stimulat- 

 ing processes actually revive or rejuvenate worthless seeds 

 to a greater extent than would result from the most favor- 

 able conditions for germination. 



Sterilized subsoil, or that lacking in humus, has the same 

 effect on germination as sterilized loam rich in organic mat- 

 ter ; but it inhi))its gi'owth to a very large extent, thereby 

 differing in this respect. It would appear, therefore, that a 

 considerable amount of humus is necessary in soils, in order 

 that they may be materially benefited by sterilization. 



The reason that bacteria multiply more and })lants grow 

 much more luxuriantly in sterilized soils is undoubtedly due 

 to the fact that a larger amount of available material for 

 plant development is present. Why subsoils and those poor 

 in organic matter give rise to a greatly inhibited growth is 

 not so clear at present, and Ave are not prepared to oiler 

 any explanation of this phenomenon. 



