QUESTION OF THE SOUECES OF THE NITROGEN OF VEGETATION. 
97 
sandy soil where lupins were growing well, and root-nodules were then abundantly 
produced. 
The amounts of produce recorded seemed to leave no doubt that they contained 
much more nitrogen than was supplied in the seed ; whilst the amount added in the 
soil-extract was quite immaterial. The negative result with Graminese, with peas 
under sterilised conditions, or in sand not seeded with rich soil-extract, and with 
lupins in sand not seeded, or seeded with the rich soil-extract, and, on the other 
hand, the positive result with peas in the seeded sand, and with lupins when the sand 
was seeded with an extract from a suitable soil, seemed to exclude the supposition of 
any other source of gain than the fixation of free nitrogen under the influence of 
micro-organisms ; and at first Hellriegel was disposed to connect the action with 
the root-nodules and their contents. 
WiLFARTH gave the results of a subsequent season’s experiments, which fully 
confirmed those recorded by Hellriegel, both as to the negative result with other 
plants, and to the positive result with Papilionaceee. Peas grew luxuriantly when 
the nitrogen-free soil was seeded with the watery extract from any cultivated soil, 
but serradella and lupins only when seeded with an extract from soil where these 
plants were growing. 
In four experiments with lupins nearly 50 times as much dry substance was 
produced, and nearly 100 times as much nitrogen was assimilated, with, as without, 
seeding with the soil-extract ! 
WiLFARTH concluded that the Papilionacese can derive the whole of their nitrogen 
from the ah*, but that it is doubtful whether the root-nodules are connected with the 
fixation, though the results point to the agency of bacteria in some way. 
In reference to these results, whilst it can hardly be said that there is any unsolved 
problem in regard to the source of the nitrogen of other than our leguminous crops, 
it must be admitted that in spite of all the investigations and discussions of the last 
50 years, the source of the whole of the nitrogen of these crops has not been satis¬ 
factorily explained by results obtained on the lines of inquiry until recently adopted. 
Evidence obtained on new lines should therefore receive careful consideration ; and 
there can be no doubt that in recent years cumulative evidence has been adduced 
indicating that certain chlorophyllous plants may avail themselves of nitrogen brought 
into combination under the influence of lower organisms; the development and action 
of which would seem in some cases to be a coincident of the growth of the higher 
plants to be benefited. But such a conclusion is of such fundamental importance 
that further confirmation must yet be demanded before it can be corsidered to be 
fully established. 
So long ago as 1853, Professor Emil von Wolff obtained 6 times as much dry 
produce of clover, grown in an ignited rich meadow soil, as in the same soil in its 
natural state. Thus, the increased growth, and the increased assimilation of nitrogen, 
took place in a soil not only nitrogen-free, but sterilised ; so that, unless micro- 
MDCCCLXXXIX. —B. 
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