THE ACQUISITION OF ATMOSPHERIC NITROGEN. I23 



ARE THERE SEVERAL SPECIES OF NODULE-PRODUCING ORGAN- 

 ISMS? 



The fact that many different forms of bacteroids have been 

 noted among the different species of legumes, has led to the view 

 that each species of leguminous plant may have its specific 

 nodule-producing bacterium. In nitrogen-free soils, as shown 

 by Nobbe and Hiltner,* Lupinus luteiis, L. augitstifolius and some 

 of the Acacias, produce tubercles when inoculated with bacteria 

 of pea and bean tubercles, but when nitrogen was present in the 

 soil, no infection occurred; an indication that nitrogen hunger 

 is an important factor. 



Bolley has observedf that many of the introduced legumes, 

 especially Trifolium pratense, often fail to establish themselves 

 in the virgin soil of the prairie, even though native leguminous 

 species may be abundant. On the other hand, when preceded 

 by Trifolium repens, the red clover develops tubercles and is 

 thrifty. 



Schneider:!: has classified the various forms under the general 

 name of Rhizobkim, adopting the generic name suggested by 

 Frank. § This classification is based mainly on form, but cul- 

 tural characteristics have since been ascribed to several of these 

 forms. 



Byerinck made numerous artificial cultures and claims** that 

 different races were obtained which remained true to form 

 through successive cultures. 



Nobbe, Schmid, Hiltner and Hotteryj found that "Lupinus 

 luteiis inoculated with pea tubercle organisms, as well as those 

 from Robinia, Cytisus and Gleditschia, developed no tubercles, 

 but when inoculated with lupine tubercle organisms, developed 

 tubercles. Phaseolus vulgaris inoculated with cultures from 

 tubercles of Phaseolus and peas developed tubercles, but if 

 inoculated with cultures from tubercles of Lupinus or Robinia 

 none were developed. In one case Pisum sativum inoculated 



*Landw. Vers. Stat. 39, 227-359 (1893). 



fAg. Sci. 7: 58, (1893). 



J Bui. Torrey Bot. Club XIX 203, July 1S92. 



§Ueber die Pilzesymbiose der Leguminosen, Berlin 1S90. 



**Bot. Zeit. 1SS8; cited by Atkinson, Bot. Gaz. 18: 262. 



tfLand-w. Versuchs Stat. XXXIX (1891), 227-359. 



