22 THEORIES ON THE ABSORPTION OF NITROGEN 



and organic nitrogen upon whicli it lives, and from wliich, 

 at the same time, it draws the energy necessary to fix the 

 free nitrogen destined, as j\I. Nobbe says, to be placed in 

 assimilable form at the disposition of the plant. 



" To place this organism in a mediimi devoid of nitrogen 

 in combination is to force it to nourish itself at the expense 

 of atmospheric nitrogen. It must, first of all, ensure its 

 survival, and this it does by multiplying at the expense of 

 the resources stored up in the plant's cotyledons while 

 awaiting the formation of those organs of the plant which 

 enable it to derive its nourishment from the soil and 

 atmosphere. 



" The free access of air exerts a most favourable influence 

 on the fixation of nitrogen." 



The authority of the writer and the rational arguments 

 arising from his experiments confirm the theory concerning 

 the occurrence of bacteria in the nodules of LeguminoSc'e. 



The works of Maze followed those of Breal, Schloesing, 

 Laurent, Beijerinck, and Praznowski. 



We shall next see how ITellriegel and Wilfarth arrived 

 at the same conclusion. 



The Work of Hellriegel and Wilfarth. 



As early as the year 1862, Hellriegel, in collaboration 

 with Drs. Fittbogen, Fruhling, Sorauer, and Marx, under- 

 took, at the Agricultural Station at Dahme, a series of 

 experiments on the Gramincce and Leguminosae. They 

 came to the conclusion that the Graminect were unable to 

 grow in a soil devoid of nitrogen, once the nitrogen con- 

 tained in the seed had been exhausted by the plant. Also, 

 whenever these plants were furnished with nitrogenous food 

 their development was normal, whereas in proportion as the 

 nitrogenous diet was diminished so did the relative crop 

 decrease. 



