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Sir J. B. Lawes and Prof. J. H. Gilbert. [Jan. 9, 



none. The inoculated plant also contained about two and a half 

 times as much nitrogen as the seed, whilst without inoculation there 

 was practically no gain. This experiment has been repeated by 

 Hellriegel with very striking results, as one of us had the oppor- 

 tunity of seeing in August last. In another experiment, peas were 

 germinated in a lucerne soil, transplanted into gravel, and nutritive 

 solution free from nitrogen added, when the roots became covered 

 with tubercles, and the nitrogen assimilated was nearly twenty-five 

 fold that of the seed. On inoculating the germinated roots of 

 haricots, and planting them in sand, they grew vigorously, formed 

 pods, developed many tubercles on their roots, and assimilated nearly 

 fifteen times as much nitrogen as the seed supplied. Lastly, he 

 planted a fragment of lucerne root with nodules on it, in a sandy soil, 

 reserving a similar fragment for analysis. Several cuttings of 

 lucerne were obtained ; and when taken up the root had many 

 nodules, and the nitrogen assimilated was more than eighty times as 

 much as in the root planted. 



As to the importance to agriculture, in a quantitative sense, of 

 this newly established source of nitrogen to the Leguminosse, the 

 evidence at present at command is insufficient to enable us to form, 

 any very decided opinion. Both agricultural investigation and direct 

 vegetation experiment have clearly shown that Leguminosaa do take 

 up much soil-nitrogen, and, at any rate in great part, as nitrate. But 

 in our recent paper in the ' Philosophical Transactions ' before referred 

 to, we showed that, in some special cases, there was no evidence to 

 justify the conclusion that the whole of the nitrogen had been so de- 

 rived ; and it was admitted that some other explanation of the large 

 amounts of nitrogen assimilated was needed. It is not improbable 

 that, in those cases, the agency now under consideration contributed 

 to the result. 



Then, as to the growth of leguminous crops in the ordinary course 

 of agriculture. Hellriegel agrees with us that they do utilise soil- 

 nitrogen, and he thinks probably always first ; but that that source 

 is supplemented by nitrogen brought into combination under the 

 influence of the symbiotic growth of special organisms and the higher 

 plant ; and he supposes that the proportion of the total nitrogen assi- 

 milated which will be due to this latter source will be greater in crops 

 grown in soils that are poor than in those which are rich in nitrogen. 

 He considers it probable, however, that even in the case of rich soils 

 there will be always more or less gain due to such fixation. The pro*- 

 portion of the nitrogen assimilated which will be gain depends, there- 

 fore, on complicated conditions. As bearing upon this subject it may 

 be stated that, in experiments with beans, Professor Vines found 

 that the formation of tubercles on the roots was very much reduced, 

 if not indeed only accidental, when the plant was liberally supplied 



