TRANSACTIONS OF SECTION B. 



685 



now described, will, it is hoped, shortly appear in the Journal of the Chemical 

 Society of London. 



3. On the Assr.ntlafion of AfmospJieric Xi'trogcn lij Plantg. 

 Ihj Professor W. O. Aj water. 



Plants ('(hvarf ]ioas) -were cultivated in purified sand to ■which 'were added' 

 nutritive .solutions with known ([uantities'of nitrofren in forms of potassium and 

 cnlriimi nitrates. The amounts of nitroiren supplied in solution and seed were com- 

 pared with amounts fnund at the end of the experiment in residual solution and 

 jilants. The excess of the latter over the former must represent nitrogen acquired 

 from the atniosjihere. 



A number of trials were made, with varyincr degrees of concentration of the 

 nutritive solutions, with ditleront amounts of food per plant, and with larger and 

 smaller supplies of nitrogen in the solution ; the nVy it being to test the eflt'Ct of 

 normal and abnoi'nial conditions upon the acquisition of atmospheric nitrogen by 

 the plants. Tu concentrated s:ilutions, wliich are hnowii to bo prejudicial Xo- 

 assimilation, tjie plants acquired little or no nitrogen from the air. 



In the moderately dilute solutions, however, whose concentration was such as 

 has elsewhere been found favourable to healtliy growth, the nitrogen of the jdants 

 largely exceeded that supplied by nutritive sfilution and seed, and is shown by the 

 followiii"' figures : — 



TI)at is to say, in four trials with solutions sufllciently dilute to permit normal 

 assimilation, the very poorly fed plants obtained over (uie-third, and the tolerably 

 well fed ones, one-half, their whole nitrogen from the atmosphere. 



The plants acquired a milligramme i if nitrogen from the t'ir, for every milligramme- 

 taken from the solution and seed. And what is even more noticeable, not only 

 where the amount of nitrogen supplied was very small did they do this, but also 

 where it was more than twice as large. The results show very clearly tliat the 

 assimilation of nitrogen decreased with the concentration of the solution, and with 

 the reduction of the supply of total food, or of nitrogen in the food. In other 

 words, the acquisition of aerial nitrogen was greater in ]n'0])ortion as the conditions 

 of p-rowtl< were more nearly normal. This fact is of interest in vieAv of the cir- 

 cumstance that the experiments upon which the belief that idants acquire little or 

 no free nitrogen from the atmosphere is based, have been made under conditions 

 more or less abnormal. 



The experiments do not show whether the nitrogen acquired from the atmos- 

 phere was combined or free nitrogen. It is, however, very dillicult to lielieve 

 tiiat so much nitrogen could have been gathered from the nitrogen compounds,, 

 ammonia, nitrates, nitrites, &c., of the atmosphere. 



m 



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i^lf. 



