AS NITROGEN GATHERER^ 23 



In experimental work at the New Jersey experi- 

 ment station, Doctor Halsted* found that in many 

 instances there was a decided increase in yield of 

 beans on soils where several successive crops of 

 beans had been grown, over the yield grown on a 

 soil for the first time. The roots of the plant growing 

 on old ground were supplied with rather abundant 

 tubercles, with the exception of a plat which was 

 shaded. Here the tubercles were much less abun- 

 dant. In the new soil the tubercles were usually 

 almost entirely absent, and during days of thinning 

 the plants (about 12 days after planting), almost 

 none were observed. At the same time they were 

 very abundant upon the plants in the old ground. 

 This seems to indicate that the root tubercle or- 

 ganisms were present in unusual amounts in the old 

 land, and in comparatively limited amount on the new 

 land. 



Pea and bean tubercles not identical. Compari- 

 sons were made between the tubercles on the roots 

 of beans and peas by Doctor Halsted, who found the 

 differences in structure and external appearances 

 were so striking as to suggest almost separate 

 origin. The differences in root system of the two 

 plants, however, would probably account for the 

 difference in form of tubercles in a degree. 



Artificial inoculations of beans with pea tubercle 

 bacteria, by Nobbe and Hiltner** were made in 1900. 

 Reciprocal inoculations were made on beans and 

 peas with bacteria from the tubercles of each, the 

 object being to ascertain the effect of the adaptation 

 of the organisms to plants of a different genus than 

 that from which they were originally secured. It 



*Proc Soc Prom Agri Sci 1897, pp 78-81. **E S R, Vol 12. 



