232 HOW CROPS FEED. 
Do the Organic Matters of the Soil Directly Nourish 
Vegetation ?—This is a question which, so far as humus is 
concerned, has been discussed with great earnestness by 
the most prominent writers on Agricultural Science. 
De Saussure, Berzelius, and Mulder, have argued in the 
affirmative; while Liebig and his numerous adherents to- 
tally deny to humus the possession of any nutritive value. 
It is probable that humus may be directly absorbed by, 
and feed, plants. It is certain, also, that it docs not con- 
tribute largely to the sustenance of agricultural crops. 
To ascertain the real extent to which humus is taken up 
by plants, or even to demonstrate that it is taken up by 
them, is, perhaps, impossible from the data now in our 
possession. We shall consider the probabilities, 
There have not been wanting attempts to ascertain ex- 
perimentally whether humus is capable of feeding vegeta- 
tion. Hartig, De Saussure, Wiegmann and Polstorf, and 
Soubeiran, have observed the growth of plants whose 
roots were immersed in solutions of humus. The experi- 
ments of Hartig led this observer to conclude that humate 
of potash and water-extract of peat do not enter the roots 
of plants. Not having had access to the original account 
of this investigation, the writer cannot, perhaps, judge 
properly of its merits, It appears, however, that the 
roots of the plants operated with were not kept constantly 
moist, and their extremities were decomposed by too great 
concentration of the liquid in which they were immersed. 
Under such conditions accurate results were out of the 
question. , 
De Saussure (Ann. Ch. u. Ph., 42, 275) made two ex- 
periments, one with a bean, the other with Polygonum 
Persicaria, in which these plants were made to vegetate 
with their roots immersed in a solution of humate of pot- 
ash (prepared by boiling humus with bicarbonate of pot- 
ash). In the first case the bean plant, originally weighing 
11 grams, gained during 14 days 6 grms., while the 
