BACTERIA FIXING ATMOSPHERIC NITROGEN 123 



origin from the atmosphere." Boussingault 94 was the first to carry out 

 a series of systematic studies on the nitrogen nutrition of leguminous 

 and cereal plants. He established the fact that, in the cultivation of 

 clover in unmanured soils, there is a definite gain, not only of carbon, 

 hydrogen and oxygen, but also of large quantities of nitrogen; wheat, 

 however, under the same conditions shows no gain or loss in nitrogen. 

 Boussingault definitely expressed his opinion that nitrogen belongs to 

 those elements which leguminous plants (clover, peas) can assimilate from 

 the atmosphere, while cereal plants (wheat, oats) cannot do so. In 

 attempting to repeat these experiments under more carefully controlled 

 conditions, Boussingault ignited the sand (thus killing the bacteria) and 

 found that neither cereals nor legumes were capable of assimilating 

 atmospheric nitrogen. 95 



In an elaborate series of experiments begun in 1857 at the Rothamsted 

 Experimental Station, Lawes, Gilbert and Pugh 96 were so careful 

 to eliminate any possibility of the plants obtaining any combined 

 nitrogen from the atmosphere, that they destroyed the organism fixing 

 the nitrogen symbiotically with leguminous plants; they thus failed to 

 become the discoverers of this symbiotic relationship, since, in the 

 absence of the bacteria, the leguminous plants behaved like the cereals 

 and could not utilize the atmospheric nitrogen. Breitschneider 97 

 demonstrated in 1861 that legumes do not fix any nitrogen when the soil 

 is ignited but do so in unignited soil. Schulz-Lupitz 98 grew lupines for 

 fifteen consecutive times, without the application of nitrogen fertilizer 

 and without diminishing yields; cereals following lupines gave much 

 higher yields than on the same land not preceded by the leguminous 

 crop; the nitrogen content of the soil was actually found to increase. 



The presence of nodules on the roots of leguminous plants was re- 

 corded by Malpighi 99 as early as 1687, but he, as well as others, con- 



94 Boussingault. Recherches chimiques sur la vegetation enterprises dans le 

 but d'examiner si les plantes prennent de l'azote de l'atmosphere. Compt. Rend. 

 Acad. Sci.6: 102-112. 1838; 7: 889-892; Ann. Chim. et phys. (2), 67: 1-54 1838; 

 69: 353-367. 1838; Compt. Rend. Acad. Sci. 38: 580-607. 1854; 39: 601-613. 



96 Ville. Note sur l'assimilation de l'azote de l'air par les plantes. Compt. 

 Rend. Acad. Sci. 31: 578. 1850; 35: 464-468, 650-654. 1852; 38: 705-709, 723- 

 727. 1854;43:143-148. 1856. 



96 Lawes, Gilbert and Pugh, 1861 (p. 106). 



97 Breitschneider. Kann der freie Stickstoff zur Bildung der Leguminosen 

 beitragen? Jahresber. Agr. Chem. 4: 123. 1861. 



98 Schultz, L. Reinertrilge auf leichtem Boden, ein Wort der Erfahrung, zur 

 Abwehr der wirtschaftlichen Noth. Landw. Jahrb. 10: 777-848. 1881. 



99 Malpighi. Opera omnia. Anatomia plantarum, Pars II. De gallis. 1687, 

 126. 



