26 



THEORIES ON THE ABSORPTION OF NITROGEN 



Years 



Influence of a Boiled Soil Infusion. 



Numbers 



of the 



vessels 



1887 



In sterilized soil 



1S87 

 In sterilized soil 



to which a 

 boiled soil infu- 

 sion had been 

 added 



322 



323 

 324 

 356 

 357 

 358 



328 

 329 

 330 



359 

 360 



361 



The authors conchided from these observations lliat the 

 accumulation of nitrogen in the Leguminosas is the work of 

 micro-organisms; indeed, tlianks to the foregoing experi- 

 ments, we are forced to acknowledge that this assimilatif)n 

 rests on a symbiotic relationship of these plants, which 

 exerts a great influence on their vital functions. 



The experiments of I^erthelot showed that an uncultivated 

 soil possessing certain cjualities favourable to the develop- 

 ment of bacteria was able to add to and keep its stock of 

 nitrogen, while those of h'ranck proved that similar increase 

 might result from the ANork- of alga? and mosses. While 

 giving full -weight to these considerations, Hellriegel cannot 

 think that they are sufficient to clear up the cjuestion of the 

 assimilation of nitrogen in his experiments. 



For instance, it would be difficult to explain how peas 

 are able to assimilate this nitrogen, whereas oats and barley, 

 with a period of growth ecjually long, are unable to derive 

 profit from this source. Again, how can one explain wln- 

 the addition of a small dose of soil infusion exerted no in- 

 fluence whatever on the growth of lupins and serradellas, 

 whereas the same cjuantitv assisted that of peas? It is true, 

 the difference in species might be invoked in order to explain 

 their unequal capacity to utilize this nitrogen, but such an 

 assertion, say the authors, is not founded on an\' known 

 fact, nor is it confirmed by practice. 



