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work on the bacteriological relations of the manure, elsewhere reported, reached 
this conclusion. “Bacteria are in no way responsible for the beneficial action of 
the manure on the growth of the clover, for in the first place it was shown that 
sterile manure was as beneficial as the unsterilized, and in the second place 
it was shown that when the whole pot was sterilized the crop did not suffer, 
but was even a little better.” Therefore it was not on account of the bacteri- 
ological relations that the manure did not nourish the clover when grown in 
the sand. 
The following points are proven: 500 c. c. of manure leachings when applied 
to a pot of the soil under study, caused a remarkable growth of the clover dur- 
ing the first two months of its life. The nutrient solution when applied to this 
soil helped the clover finally, but the help was very tardy in coming. 235 c. c. 
of the manure extract (in two portions) when applied ro the same sized pot 
containing an equal number of clover plants, but filled with the quartz sand, 
failed to feed the clover, but on the contrary poisoned it. The nutrient solu- 
tion in this same sand caused a perfect normal growth. 
The problem of the action of the manure on the soil has been narrowed 
down to the plant food or the antitoxic action of the manure. By taking the 
manure and the clover away from the soil and placing them in this neutral 
sand, it is easy to see how the manure affects the clover. If the manure fed 
the clover in the soil it should do the same in the sand. If the soluble organic 
matter in the manure was used directly by the clover and was better suited to 
it than mineral food, then the plants fed by the manure should have surpassed 
the plants fed by the mineral food when they were both grown in the sand. 
The failure to do so proves that the clover does not use the soluble organic 
matter as food, and the remarkable growth of the clover treated with manure 
when grown in the soil is not due to the plant food found in the manure. 
Looking at the question from the side of the soil, the theory that the soil 
experimented with was a poor medium for the growth of clover simply for the 
lack of readily available plant food, and that the manure supplied this, is untrue. 
The sand experiment showed that the nutrient solution was a good plant food, 
but when this was applied to the soil the help it gave the clover plant v/as 
very tardy. On the other hand the manure is shown not to be a good plant 
food by itself, but when applied to the soil the benefit received from it was 
immediate and striking. 
The only explanation left for the action of the manure on the soil, is the 
toxin theory. There were toxins in the soil which were neutralized by the 
manure and this purified the soil, making it a good medium for the growth of 
clover. When the clover was grown in the sand, no toxins being present to 
neutralize, the antitoxin in the manure w^as an injury to the clover. The soil 
pots that were treated with mineral fertilizers apparently had the toxins cor- 
rected by the combined action of the clover roots and the chemicals, but this 
was a slower process than the action of the manure. That this action can 
take place has been demonstrated by the work of the Bureau of Soils.^ 
THE TOXIC ACTION OF COCKLEBUES. 
The previous study has shown that there is a toxin in the soil which is 
being investigated. This toxin may have arisen from various sources and it is 
possible that it may have come from some of the weeds which grew in the 
^Bull. 47, Beureau of Soils, U. S. Dept. Agri. 
