72 
SIR J. B. LA WES AND PROFESSOR J. H. GILBERT ON THE 
As to the results, Wolff called attention to the fact that with the oats and the 
potatoes comparatively little increase was obtained by the use of mineral manure 
without nitrogen, but that where nitrogenous manure was added the increase bore a 
direct relation to the amount of nitric-nitrogen supplied. The behaviour of the 
Leguminosse was, however, quite different. With these plants, the mineral manures 
as a rule gave considerable increase, whilst the addition of the nitrate generally gave 
little or no further increase. He remarks that these results are consistent with those 
obtained in ordinary agriculture; and that it is a question whether the so-called 
“ nitrogen collectors ” obtain all their nitrogen by means of their widely and deeply 
penetrating roots, or whether they draw some of it from the air; and if so, whether 
they can only take it as combined nitrogen, or also as free nitrogen ? He considers 
that the results of Boijssingault and ourselves are against the supposition that they 
assimilate free nitrogen. At the same time he thinks the results of Hellriegel 
show that the Papilionaceae are not dependent on soil sources of nitrogen alone; 
though further evidence is required to determine whether or not the free nitrogen of 
the air comes into play. 
As to the connection of the root-nodules with the development of the plants, Wolff 
considers that they may be equally well supposed to be a consequence as a cause of 
active growth. Observations by Schultz-Ltjpitz, and at Hohenheim, have shown 
that the nodules may be very little developed in a soil rich in nitrogen. He refers 
to the results of Frank and Brunchorst, as indicating, that the contents of the 
nodules do not consist either of bacteria or of fungoid forms,but rather of nitrogenous 
matters which are re-absorbed by the plant when forming fruit. 
As bearing on the subject, he quotes the following results of Troschke at Begen- 
walde, showing the comparative composition of the nodules and of the roots of blue 
lupins, at the time of pod formation : — 
Nodules 
Roots .... 
Pure ash. 
Crude fat. 
Crude fibre. 
Crude 
protein. 
Non¬ 
nitrogen ous 
extract. 
Nitrogen. 
Of total 
nitrogen 
albuminoid. 
Per cent. 
7-51 
4-07 
Per cent. 
5-.33 
I-3I 
Per cent. 
9-43 
52-25 
Per cent. 
45-31 
7-06 
Per cent. 
32-42 
34-61 
Per cent. 
7-25 
1-13 
Per cent. 
69-7 
73-7 
At Hohenheim, the nodules of yellow lupins were found to be less nitrogenous at 
the conclusion of pod-formation. 
Wolff cousiders that numerous results show that atmospheric sources of nitrogen 
do come into play in the growth of the Papilionacese. He quotes from Boussingault 
in reference to experiments with clover and peas grown in a nitrogen-free soil that 
* It may be observed that the recent results of Professor M4RSHall Ward (‘ Phil. Trans.,’ B, vol. 
178,1887, pp. 539-562) are at variance with the views of Frank, Brunchorst, and Tschirch on this point. 
