QUESTION OF THE SOURCES OF THE NITROGEN OF VEGETATION. 
29 
One weighed portion of the pulp was put on the vacuum filter as before, and 
another was submitted to dialysis, the diluted pulp being put into a parchment paper 
sausage dialyser which was then placed in pure distilled water. However, neither 
the vacuum filtrate nor the dialysate was quite clear. Both these extracts showed a 
less degree of acidity, and it was evident that the root was now in a very inactive 
state compared with that of the specimens collected early in September. Various 
qualitative examinations were made, and it was found that the extracts contained a 
large amount of nitric acid. It was decided, however, that further detailed investi¬ 
gation of the subject must be postponed until the return of the actively growing 
period. 
It was intended to undertake the subject in the spring and summer of 1886, but 
owing to the pressure of other work nothing more was accomplished than the com¬ 
parative testing of the acidity of the sap of the inots of a number of plants representing 
very various natural families. The matter was, however, again taken up in April, 
1887; and, benefiting by previous experience, some advance was made, but still the 
attempts to entirely free the acid extract from nitrogen were not successful. 
It is of interest to observe that the degree of acidity of the sap of the roots 
collected in April, May, and June, that is during the periods of the most active 
growth of the season, was considerably higher than in that of the roots collected in 
September, 1885, after the cutting of the first crop. 
The investigation is, however, at present little more than commenced, and any 
further reference to the results must be postponed to some future occasion. 
7. Action of Dilute Organic Acid Solutions on the Nitrogen of Soils and Subsoils. 
In the autumn of 1885, when it was found necessary to postpone further experi¬ 
ment with the acid root-sap, it was decided in the meantime to examine the action on 
soils and subsoils, of various organic acids, in solutions of a degree of acidity either 
approximately the same as that of the Medicago sativa root juice, or having a known 
relation to it. The acids experimented upon were the malic, citric, tartaric, oxalic, 
acetic, and formic. 
In the first experiments, pure water, and dilute solutions of malic, citric, tartaric, 
oxalic, and acetic acids, were used; each of the acid solutions being of approximately 
the same degree of acidity as the sap of the Medicago sativa roots collected in 
September, 1885, that is after the removal of the first crop, which represented the 
greater part of the growth of the season. The subsoil employed was a mixture of 
the sifted soil of the fifth, sixth, seventh, eighth, ninth, and tenth depths of 9 inches 
each, from the unmanured wheat-fallow land immediately adjoining the leguminous 
plots, and contained, as dried at 100° C., 0'047 per cent, of nitrogen. 
The mixtures were made in wide-mouthed stoppered bottles, in the proportion of 
200 grams of the subsoil to 1000 c.c. of the water or acid solution. After being well 
