FROM lllK AIR BY THE LEGUMINOS^ 2^ 



All these phenomena, and others still more complex, are 

 in no way mysterious if it be admitted that certain higher 

 plants are in intimate relationship with micro-organisms 

 which collect nitrogen and thus perform this useful work. 



Without denying the work of bacteria, algcC and fungi, 

 which fix nitrogen, Hellriegel wishes simply to demonstrate 

 that the gain in nitrogen cannot proceed from this source 

 alone. Indeed, in his experiments, the fact that lupins and 

 serradellas were furnished with large quantities of algai and 

 mosses of all kinds did not preyent them from perishing 

 of nitrogen hunger. 



Certain anomalies which arose during the course of trial 

 growths in 1887 led the authors to think that sterilization 

 had played an important part in connection with the appear- 

 ance of mosses and algai on the sides of the vessels con- 

 taining the earth. In those vessels which had been sterilized 

 this growth appeared only after the lapse of several weeks, 

 and had no effect on lupins and serradellas, Avhile it 

 accelerated the growth of peas. They concluded tiiat the 

 same soil infusion had different actions on lupins and peas, 

 and explained these phenomena as follows. 



If it be true that the growth of Leguminosai in soils 

 devoid of nitrogen is the result of this symbiosis A\ith micro- 

 organisms, it must be admitted that each leguminous plant 

 has its own particular species of such micro-organisms, and 

 as these different species of bacteria are not equally dis- 

 tributed throughout all soils, we have the reason why the 

 same soil infusion does not act in ecjual manner on both 

 lupins and peas. Since these variations cannot arise from 

 the physical or chemical properties of the soil, they must 

 be due to differences in the bacterial population. 



Hellriegel and Wilfarth expressed the opinion, before a 

 meeting of German naturalists, that the tubercles of Legu- 

 minosas played an important part in assimilating nitrogen. 

 Finding this opinion subjected to a considerable amount of 

 criticism, they undertook a series of experiments which 



