QUESTION OF THE SOURCES OF THE NITROGEN OF VEGETATION. 
31 
extracts were made, one. by the soda-lime method, and the other by Kjeldahl’s 
sulphuric acid method. 
In the following Table the results obtained in these experiments by Kjeldahl’s 
method are given. 
Table XI.—Showing the amount of the Nitrogen of surface soil and subsoil dissolved 
by malic acid solution of approximately twice the acidity of the sap of the 
Medicago sativa roots collected in September, 1885. 
9. 
Nitrogen dissolved per million soil. 
After 1 hour’s contact. 
After 24 hours’ contact. 
400 grams soil, 1000 c.c. acid solution, each extraction. 
iTTi i n ^ -1 r First extraction. 
VV iiGtiu-icillo w subsoil VO 1 X L* 
oGCOUCl GXtrclctlOll .... 
T p -T r First extraction. 
Lucerne suriace sou s c- j i. x- 
L becond extraction .... 
Per million. 
2-43 
2T9 
9-72 
6-08 
Per million. 
1-82 
2T9 
8-51 
7'S9 
200 grams soil, 1000 c.c. acid solution, each extraction. 
-ixTi, j. r 11 1 -if First extraction. 
VV heat-tailow subsoil < ^ i x x- 
[ becond extraction .... 
r n -if First extraction. 
Lucerne suriace soil < o ^ . ,■ 
1 becond extraction .... 
3- 28 
4- 03 
8-14 
4-35 
7-29 
3-61 
10-81 
7-31 
First as to the experiments the results of which are given in the upper division of 
the table, in which 400 grams of soil were mixed with 1000 c.c. of acid solution, in 
each extraction, that is to say, after the removal of the first extract by decantation 
and the filter pump, a second quantity of the acid solution was added. After 
1 hour’s contact with the subsoil, the liquid remained only slightly acid, and the 
amount of nitrogen taken up was very small, representing only 2'43 parts per million 
of subsoil. After 24 hours’ contact the liquid was still less acid, and the amount of 
nitrogen found in the extract was, calculated per million of subsoil, considerably less 
than after only I hour’s contact. 
After the addition of a second quantity of the acid solution to the already once 
extracted subsoil, the liquid remained much more acid than in the case of the first 
extraction, both after 1 hour’s and 24 hours’ contact. Still, the amount of nitrogen 
taken up was very small; being only 2T9 per million soil after 1 hour’s, and the same 
after 24 hours’ contact. That is to say, with the greater remaining acidity in the 
second extraction, there was not less nitrogen taken up after 24 than after 1 hour’s 
contact. It may be observed that, under these conditions, much more total matter, 
remained dissolved in the second than in the first extract. 
