APPLICATEON OF SCIENCE TO PLANT CULTURE. 87 



The faculty of obtaining nitrogen from the air appears to be 

 especially characteristic of the legumes. By what species of leg- 

 umes or other families of plants it is possessed, it is, as yet 

 impossible to say. 



But, whatever may be the plants that acquire atmospheric 

 nitrogen, the ways by which they acquire it, or the form in which 

 it comes, the fact of its acquisition in considerable quantities 

 seems well established." 



The object of these experiments was to answer the question, 

 Suppose we give our plants a little nitrogen, can they supply the 

 rest? 



A French scientist made some experiments in which he found 

 that, under the influence of electricity, nitrogen might be assimi- 

 lated. 



The belief that no considerable quantity of atmospheric nitrogen 

 may be used by the plant is too deep-rooted to be easily put 

 aside. There is a certain conservatism — and it is a wise conserv- 

 atism — which makes people verj^ slow to accept results opposed to 

 old and well-established beliefs. It was with no little interest, 

 therefore, that chemists and vegetable physiologists read an 

 account of the paper presented by Professor Hellriegel, at the 

 meeting of the German Naturforscher-Versammlung in Berlin in 

 1887, announcing experiments in which leguminous plants were 

 found to obtain large quantities of nitrogen directly from the air, 

 under conditions which led him to believe that they assimilated 

 free nitrogen b}^ the aid of micro-organisms. He said (I trans- 

 late freely from the report) : 



" The papiliouacese are not dependent upon the soil for the 

 nitrogen of their food. The source of nitrogen which the atmos- 

 phere offers can alone suffice to bring them to normal, indeed 

 luxuriant, development. It is not the small quantities of the 

 combined nitrogen in the air which supply the papilionaceae with 

 nutriment, but the free nitrogen of the air comes into play ; and 

 there is a direct relation between the assimilation and the nodules 

 on the roots of the leguminous plants. That is, the growth of the 

 papilionaceae in soil free from nitrogen can be caused at will by 

 the addition of small quantities of cultivated soil and can be hin- 

 dered by excluding micro-organisms." 



In Helhiegel's experiments, lupines started in a soil free from 

 nitrogen did not grow well, but when an infusion of ordinary soil 



