14 THEORIES ON THE ABSORPTION OF NITROGEN 



tubes, nor by passing the nitrogen through water, nor by 

 varying the proportions between the reacting substances, 

 nor by exposing the soil to an atmosphere deprived of oxygen, 

 was he able to obtain nitrogen fixation as a result. 



French scientists have not been alone in devoting atten- 

 tion to these problems. We also have the researches of 

 Dietzell, Atwater, Strecker, Franck, Wolf, &c. Atwater 

 used a calcined river sand in which he planted peas. 

 These peas were nourished by nutritive matter in solution 

 containing calcium and potassium nitrate in varying pro- 

 portions. In twenty cases the results gave twelve times 

 more nitrogen than had been present at the start in the seed, 

 or conveyed to it by matter in solution. 



Wolf employed a river sand greatly impoverished by 

 washing. In some instances he used no manure, in others 

 he added a nutritive mixture devoid of nitrogen, but contain- 

 ing more or less potassium nitrate. The oats cultivated 

 always yielded less nitrogen than had been supplied them 

 in the seed grain and in the manure, whilst beans, lupins, 

 and clover yielded a large surplus. 



Franck used a sandy soil containing humus with i per 

 cent, of nitrogen. One portion was left bare and others 

 were sown with lupin and clover. In those portions where 

 the vegetation was rich there was a gain in nitrogen, whilst 

 that portion which had remained unplanted, or where the 

 plant growth was feeble, showed a loss. 



Strecker experimented with oats and lupins, and stated 

 that the latter, sown without manure, acquired a remarkable 

 proportion of nitrogen, whereas the oats only showed a loss. 



Dietzell, who carried out his experiments in garden earth 

 divided into planted and unplanted allotments, proved a loss 

 of nitrogen in those which had been planted and manured, 

 whilst those left unplanted and unmanured showed an 

 increase. 



M. Joulie, a famous French scientist, cultivated buck- 

 wheat for two years in a sandy soil, manured and unmanured, 



