QUESTION OE THE SOURCES OF THE NITROGEN OF VEGETATION 
107 
organic nitrogen of the soil and subsoil into a more available condition ; whilst 
o o 
it seems not improbable that the growth and crop-residue of certain plants favour the 
development and action of special organisms. In conclusion we would submit that, 
whether or not it may eventually be conclusively proved that lower organisms have 
the power of bringing free nitrogen into combination within the soil, it would at any 
rate be not inconsistent with well established facts, were it found that the lower serve 
the higher, chiefly, if not exclusively, by bringing into a condition available to them, 
the combined nitrogen already existing, but in a comparatively inert state, in our soils 
and subsoils. 
Postscript. 
(Added October, 1888.) 
As it seemed to us that, of the various results which have been considered relating 
to the fixation of free nitrogen, those of Hellriegel and Wilfarth are the most 
definite and significant, we decided to institute experiments on somewhat similar 
lines. We hoped to commence them early in the summer, but were not able to do so 
until the beginning of August. Decisive results cannot, therefore, be expected this 
season, but the experience gained will be of value in subsequent experiments. 
This preliminary series comprises experiments with peas, blue lupins, and yellow 
lupins. The peas are grown (1) in washed sand, with the necessary mineral nutri¬ 
ment added, but with no supply of combined nitrogen beyond a small determined 
amount in the washed sand, and that in the seed sown ; (2) in similarly prepared 
sand, but seeded with the extract from a rich garden soil; (3) in the rich garden soil 
itself Each description of lupin is also grown—(l) in sand prepared as for the peas ; 
(2) in the same washed sand, seeded with the extract from a sandy soil where lupins 
had grown luxuriantly ; (3) in the lupin sandy soil itself; (4) in rich garden soil. The 
pots are all arranged in a small greenhouse. 
As the plants are still growing, no quantitative results are as yet available. It may 
be observed, however, that, so far as can be judged by the eye, there seems, in the 
case of the peas, to be somewhat more growth where the sand was seeded with the 
soil-extract, supposed to contain oi’ganistns, than where it was not; whilst in the 
cases of the lupins there is apparently even somewhat less growth with than without 
the sandy soil-extract. Both with the peas and the lupins, the growth is very much 
more luxuriant in the garden soil; and in the case of the yellow lupins it is almost as 
luxuriant in the sandy soil in which lupins had grown, as in the garden soil. These 
first experiments can obviously be only considered as initiative ; but it is intended to 
analyse the products in due course, and to undertake a new series earlier in the season 
next year. 
