360 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



tiated by the Rothamstead experiments, is quite in accord- 

 ance Avith tlie fact that, as considerable experience has shown, 

 the German potash salts are particularly useful for clover, 

 beans, vetches, and other leguminous crops. 



Is the Free Nitrogen of the Air a Source of the Nitrogen Assimi- 

 lated by Plants? 



The theory that plants can directly assimilate the free 

 nitrogen of the air was long since disposed of by the experi- 

 ments of Lawes and Gilbert, and of Boussingault. It has 

 still been maintained that free nitrogen could be oxidized 

 by the aid of ozone, and the resulting compounds direct- 

 ly absorbed by plants. Six methods for this oxidation of 

 nitrogen have been alleged: (1) by ozone assumed to be 

 evolved by plants ; (2) by contact of nitrogen with bodies 

 undergoing oxidation ; (3) during electrical discharges in the 

 air; (4) the combining of ozone with nitrogen in the pres- 

 ence of water; (5) the same in presence of bases, as alkalies, 

 lime, baryta, etc. ; and (6) through evaporation and conden- 

 sation of water in presence of air. Ville supposes that ozone 

 is evolved by plants and combines with nitrogen in solution 

 in their juices. It has been quite generally assumed that 

 nitrogen outside the plant tissues could be oxidized by ozone 

 exhaled by the plant and then absorbed by the leaves. 

 From experiments at Rothamstead, as well as from those 

 of Boussingault, Dr. Gilbert strongly doubts both the above 

 assumptions, and adds that " whether such actions take 

 place or not, it is at any rate certain that in our own experi- 

 ments we have not been able to persuade plants to avail 

 themselves of this happy faculty of producing their own 

 nitrogenous food." 



E. M.Dixon, in a "Report to the Philosophical Society of 

 Glasgow on the Production of Nitric Acid from the Free 

 Nitrogen of the Air," doubts whether the nitrogen is oxid- 

 ized by ozone in presence of bodies undergoing oxidation 

 method (2) above and as good as denies nitrification by 

 ozone in presence of water (4). Concerning the theory of 

 the formation of nitrite of ammonia (G) claimed by Scbon- 

 bein to be established by his experiments, and to explain 

 the absorption of nitrogen by vegetation, he remarks, "It 

 is, however, unfortunate . . . [for this theory] that no sooner 



