168 CONTRIBUTIONS TO OUR KNOWLEDGE OF SOIL-FERTILITY, xvi,, 



A general glance over the results leads to the belief that no 

 toxins are formed by the organisms. It may be that the excess 

 of carbonate of lime has brought about a condition in which the 

 preservation of the toxins is not possible. The outstanding 

 feature of the experiment is the increased nutritive effect ob- 

 tained with Fenicilliu'tit dados par ioides. The extract/water 

 ratio increased very rapidly, indicating that the mould had been 

 actively attacking the organic matter and producing substances 

 which stimulated the test-organism, Bac prodigiosvs. to an in- 

 creased production. 



The amount of unacted-upon carbonate in the treated leaf- 

 mould led to the belief that too much had been added, and that 

 an excess of carbonate was not desirable. 



Humus neutralised with Limk-water. 



A quantity of sifted leaf-mould was soaked in lime-water for 

 an hour, 5 litres of lime-water being used for every 500 grams of 

 leaf-mould. A trial test showed that this proportion furnished 

 a neutral extract, although, when the bulk was prepared, the 

 extract of the mould was faintly ncid. This was possibly caused 

 bv the subsequent sterilisation. iVt the end of an hour, the sus- 

 pension was stirred and decanted on to a filter, and the organic 

 matter washed, and at the same time separated from the heavier 

 sand b}' repeating the procedure with water. The residual 

 organic matter was dried, sifted, and bottled. 



At this stage, the mould contained moisture 40" 42%, asli 

 18-80%, and organic matter 40'48%, so that 24-5 grams contained 

 10 grams of organic matter. This quantity was put up into a 

 number of four-ounce bottles, which were heated for two hours 

 at 130°. Most of the moisture was driven off by the heating. A 

 test showed that the heated mould formed a coherent mass, upon 

 being pressed in the hand, when a weighed portion contained 20 

 grams of water, and this was accepted as being the quantity 

 requisite for a full bacterial growth. After the heating, the 

 water was raised to 19c.c., the remaining 1 c.c. being left for 

 the infecting suspension. The water was thoroughly incorpo- 

 rated, and the bottles were steamed for an hour. Sets were 

 infected with several micro-organisms and kept at room-temper- 

 ature, 15°. 



