

FIXATION OF FREE NITROGEN. 143 



known quantities of combined nitrogen, in the form of a solu- 

 tion of ammonium-sulphate, applied to the soil. The effect 

 of this direct supply of combined nitrogen was to increase the 

 growth in a very marked degree, especially in the case of the 

 Graminese. The figures show that the actual gains or losses 

 of nitrogen ranged a little higher in these experiments in 

 which larger quantities were involved ; but they were always 

 represented by units of milligrams only, and the losses were 

 higher than the gains. Further, the gains, such as they were, 

 were all in the experiments with the Graminese, whilst there 

 was in each case a loss with the Leguminosse, and also with 

 the buckwheat. The losses, where beyond the limits that 

 might be expected from experimental error properly so-called, 

 were doubtless due to decay of organic matter, fallen leaves, &c. 



It should be stated that the growth was far more healthy 

 with the Graminese than with the Leguminosse, which are, even 

 in the open field, very susceptible to vicissitudes of heat and 

 moisture, and were found to be extremely so under the condi- 

 tions of enclosure under glass shades. It might be objected, 

 therefore, that the negative results with the Leguminosse are 

 not so conclusive as those with the Graminese. Nevertheless 

 we concluded, and still conclude, from the results of our own 

 experiments, as Boussingault did from his, that neither the 

 Graminese nor the Leguminosse directly assimilate the free 

 nitrogen of the air. 



That, under the conditions described, the Leguminosse as 

 well as the Graminese can take up and assimilate already 

 combined nitrogen supplied to them, is clearly illustrated in 

 the experiments made in 1860 with Leguminosse alone. The 

 series comprised — three experiments with white haricot beans 

 — No. 1 without any other supply of combined nitrogen 

 than that in the seed, No. 2 with a fixed quantity of nitrogen 

 applied as ammonium-sulphate, and No. 3 with a fixed quan- 

 tity supplied as nitrate ; also three experiments with white 

 lupins — No. 1, as with the haricots, without artificial supply 

 of combined nitrogen, No. 2 with supply as ammonium-sul- 

 phate, and No. 3 was nitrate. Each of these two descriptions 

 of leguminous plant showed considerably increased growth 

 under the influence both of ammonium -sulphate and of 

 nitrate ; indeed the growth was much more satisfactory than 

 in the earlier experiments. Still, owing to the atmospheric 

 conditions within the shades, the plants lost both leaves and 

 flowers, and were, therefore, taken up earlier than they other- 

 wise would have been. The analytical results here again in- 

 dicated no gain from free nitrogen, either in the experiments 

 without, or in those with, an artificial supply of combined 

 nitrogen — in fact, the losses were greater than the gains. 



