98 
SIR J. B. LAWES AND PROFESSOR J. H. GILBERT ON THE 
organisms were acquired during growth, the supposition of their influence in fixing 
free nitroofen would be excluded. 
Much more recently Wolff has made numerous experiments with oats, potatoes, 
and various Papilionacese, in river-sand; in some cases unwashed, and in some washed; 
in some without manure, in some with purely mineral manure, and in some with 
nitrate in addition. Accordantly with common experience, there was little increase 
in the oats or potatoes with mineral, but much with nitrogenous manure ; and, on the 
other hand, with the Papilionacem there was very marked increase with the mineral 
manure, and but little more by adding nitrate. In the experiments with lupins, 
beans, and clover, in unwashed sand, the results indicated gain of nitrogen beyond 
that probably due to the nitrogenous impurity in the sand ; but with sand-peas, 
grown in washed sand, which was assumed to be nitrogen-free, the gains from some 
external source were unmistakable. 
As to the explanation, Wolff does not suppose that free nitrogen is fixed by the 
plants themselves; nor does he favour the view that it was fixed by the agency of 
micro-organisms. The plants may take up combined nitrogen from the air by their 
leaves ; but he thinks it more probable that combined nitrogen is absorbed from the 
air by the soil, and that free nitrogen is fixed within the soil under the influence of 
porous and alkaline bodies. He admits that it is not explained why cereals do not 
benefit by these actions as well as Papilionacese ; and he suggests whether the greater 
evaporation from their leaves causes greater aeration of the soil. 
Here, then, the gain of nitrogen by the Leguminosae is explained in a very different 
manner from that assumed by other recent experimenters. It seems to us, however, 
that the undoubted fact that the Gramineae, and other plants than the Papilionaceae, 
do not benefit by the actions supposed, excludes the supposition that Wolff’s results 
with Papilionaceae are to be so explained. It is true that neither in the growth of the 
clover in ignited soil, nor in that of the sand-peas in the washed sand, were the 
conditions such as would seem favourable for the presence, development, and agency 
of micro-organisms. But if, in the experiments in free air, there was no accidental 
source of combined nitrogen, it would seem that the influence of micro-organisms is at 
least as probable as that of the actions which Wolff supposes. 
Professor Atwater made numerous experiments, both on the germination and on 
the growth of peas. In eleven out of thirteen experiments on germination more or 
less loss of nitrogen was observed. In all but one out of fifteen experiments on 
vegetation, there was a gain of nitrogen, which was very variable in amount, and 
sometimes very large. As a general conclusion, he states that in some of the experi¬ 
ments half or more of the total nitrogen of the plants was acquired from the air. 
He considers that germination without loss of nitrogen is the normal process; that 
loss, whether during germination or growth, is due to decay, and therefore only 
accessory. Nevertheless, he goes into calculations of some of his own results, 
showing, by the side of the actual gains, the greater gains supposing there had been 
