51 



in No. 85 ; they are each year summarised up to date 

 in the "Memoranda;" and there are there given, also up 

 to date, the amounts of nitrogen as nitric acid in the 

 drainage-waters. 



It is a question whether a summary Table of the 

 amounts of nitrogen as nitric acid, and of chlorine, in 

 the drainage-waters from the experimental wheat-field 

 plots, could not be arranged for publication annually in 

 the " Memoranda!' Probably the subject of the amount, 

 and the composition, of rain, and of the various 

 drainage-waters, might, with advantage, be again sys- 

 tematically treated, after a period of about 10 years 

 since the former detailed publication in 1881-82. 



XIII. EXPERIMENTS ON THE QUESTION OF THE 

 FIXATION OF FREE NITROGEN. 



Experiments were commenced in 1857, and were 

 conducted for several years in succession, to determine 

 whether plants assimilate free or uncombined nitrogen, 

 and also various collateral points. 



Plants of the Gramineous, of the Leguminous, and of 

 other families, were grown, in closed vessels, under 

 sterilised conditions, supplied with pure water, washed 

 air, and carbonic acid ; in some cases without any 

 supply of combined nitrogen beyond that in the seed 

 sown, and in others with known quantities supplied 

 From the results obtained under these conditions, which 

 were such as to exclude any action either of electricity 

 or of microbes, it was concluded that, under such con- 

 ditions, our agricultural plants do not directly fix the 

 free nitrogen of the air, either by their leaves or other- 

 wise ; and although other experimenters have come to 

 an opposite conclusion from their results, we believe 

 that no evidence of a satisfactory and decisive character 

 has hitherto been adduced, which can be held as con- 

 clusive against the view which we have maintained as 

 above stated. 



In recent years, however, the question has assumed 



D 2 



