124 MAINE AGRICULTURAL EXPERIMENT STATION. 



with lupine tubercle organisms developed tubercles, while in 

 other cases it did not."* 



Laurentf found that he could produce tubercles on the roots 

 of the pea, by inoculating from the tubercles of any one of 

 thirty-six different species of leguminous plants. All species, 

 however, would not produce them in equal numbers. From 

 these and other studies he believed that there are many varieties 

 of the- organism associated with the different species of legumes. 

 It was found, however, that ordinary soil bacteria have no power 

 to produce tubercles. 



Atkinson inoculated young plants of Dolichos sinensis with 

 organisms from Vicia sativa without effect, while inoculated 

 plants of Vicia from the same culture produced tubercles. Con- 

 sidering the almost universal infection of leguminous plants, 

 however, he doubts whether there are so many species as are 

 represented by the different forms of bacteroids and suggests a 

 possible influence of the various plants on which the different 

 forms are found. "Does not the influence of the macrosym- 

 biont upon the microsymbiont while within the tubercle fix a 

 certain type of racial form and attenuation upon the microsym- 

 biont until it shall have passed through normal conditions in the 

 soil again and been restored to its original form and infecting 

 power T'% The question as yet remains open. 



FIXATION OF NITROGEN BY NON-LEGUMINOUS PLANTS. 



Some non-leguminous plants possess well developed root 

 tubercles, the function of which is, in many cases, uncertain. 

 Among such is Elaeagnus angustifoUus. This plant, as shown 

 by Nobbe and others§ is without doubt able through its root 

 tubercles, to assimilate the free nitrogen of the air. These 

 tubercles are produced by an organism entirely distinct from 

 Bacterium radicicola. In demonstrating this power of assimila- 

 tion in Elaeagnus, Nobbe planted some Elaeagnus seedlings in 

 pots containing sterilized nitrogen-free sand. The sand in one 

 pot was then inoculated with an extract of soil in which Elaeag- 

 nus had grown. No marked result was noticeable the first 



*Cited by Atkinson, Bot. Gaz. 18: 263. 

 fAnn. cl. L'Inst. Pasteur, 1891, No. 2. 

 % Atkinson, Bot. Gaz. 18: 263. (1893). 

 §Landw. Vers. Stat. 41, pp. 138-140. 



