quite a new aspect. It now is, whether free nitrogen is 

 brought into combination by the agency of micro- 

 organisms, or other low forms, either within the soil 

 itself, or in symbiosis with a higher plant ; thus 

 serving indirectly as a source of nitrogen to plants of a 

 higher order. Considering that the results of Hellriegel 

 and Wilfarth on this point were, if confirmed, of great 

 significance and importance, it was decided to institute 

 experiments at Eothamsted on similar lines. Accord- 

 ingly, a series was undertaken in 1888; and the results 

 obtained clearly indicated that there was a gain of 

 nitrogen, beyond that supplied in the combined form, 

 in the soil, and in the seed sown. These first experi- 

 ments were, however, only initiative, and new series 

 were instituted in 1889 and 1890, and some of the 

 biennial or perennial plants are still growing, so that 

 complete quantitative results are not yet available; 

 but there can be no doubt that, in the subsequent 

 experiments, the evidence of fixation will be even more 

 marked than in those of 1888. Obviously such results 

 open a wide field for further investigation; and, ac- 

 cordingly, the enquiry is being continued and extended. 

 The earlier results obtained on this subject were 

 published, in abstract in No. 14, and in considerable 

 detail in Nos. 17 and 20 (Series 1) ; and they have 

 frequently been referred to in subsequent papers. 

 Other and more recent results of our own bearing upon 

 the question, as well as those of others published within 

 recent years, have been considered, in abstract in No. 75, 

 and more fully in No. 77. A preliminary notice of 

 the results obtained in the new vegetation experiments 

 was presented to the Eoyal Society in January 1890, 

 and it is proposed to discuss them and subsequent 

 results more fully, when the whole of the analytical 

 details are available. These recent experiments on 

 the question of the fixation of free nitrogen, were 

 referred to in a postscript in No. 77, also in No. 81; 

 No. 82 gives the " Preliminary Notice ; " and No. 84 

 gives a resumd of both the earlier and the later 

 results. 



