138 THE ROTHAMSTED EXPERIMENTS. 



thirteen experiments on germination, more or less loss of ni- 

 trogen 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 experiments half or 

 more of the total nitrogen of the plants was acquired from 

 the air. 



He considered that germination without loss of nitrogen was 

 the normal process ; that loss, whether during germination or 

 growth, was due to decay, and therefore only accessory. He, 

 however, goes into calculations of some of his own results, 

 showing by the side of the actual gains, the greater gains 

 supposing there had been a loss of 15 per cent of nitrogen, 

 and still greater gains if there had been a loss of 45 per cent, 

 as in an experiment by Boussingault under special conditions. 

 Further, he says that whilst actually observed gains are proof 

 of the acquisition of nitrogen, the failure to show gain only 

 proves non-fixation if it be proved that there was no libera- 

 tion. He suggests that the negative results obtained by 

 Boussingault and at Eothamsted may be accounted for by 

 liberation; though he recognises that the conditions of the 

 experiments excluded the action of either electricity or 

 microbes. It may be remarked that, in the experiments 

 both of Boussingault and at Eothamsted, any cases of decay 

 were carefully observed, and the losses found explained 

 accordingly. It may, in fact, be taken as certain that the 

 conclusions drawn were not vitiated by any such loss. 



Atwater concluded that his results did not settle whether 

 the nitrogen gained was acquired as free or combined nitrogen, 

 by the foliage, or by the soil. He considered, however, that 

 in his experiments, the conditions were not favourable for 

 the action either of electricity or of micro-organisms ; and he 

 favoured the assumption that the plants themselves were the 

 agents. Lastly, he considered the fact of the acquisition of 

 free nitrogen in some way to be well established ; and that 

 thus facts of vegetable production were explained which 

 otherwise would remain unexplained. To this, and other 

 points involved, we shall refer again presently. 

 Heilriegd's Of all the recent results bearing upon the subject, those of 

 results. Hellriegel and Wilfarth with certain leguminous plants 

 seemed to be by far the most definite and significant, point- 

 ing to the conclusion that, although the higher chlorophyllous 

 plants may not directly utilise free nitrogen, some of them 

 at any rate may acquire nitrogen brought into combination 

 under the influence of lower organisms ; the development of 

 which is apparently in some cases a coincident of the growth 

 of the higher plant whose nutrition they are to serve. 



