24 



Journal of Agricultural Research voi. xxii. No. i 



far as number is concerned. However unsatisfactory these figures may 

 be from several points of view,' nevertheless they establish one important 

 fact beyond reasonable doubt : Modified soil temperature ^vithin the range 

 which these plants can be expected to encounter in tlie field and even 

 within which they can be grown \vith vigor under experimental conditions 

 does not prevent the infection of roots by Bacillus radicicola and the 

 formation of considerable numbers of nodules. In other words, B. radi- 

 cicola, considered as a parasite, does not show the strongly marked inhi- 

 bition of its ability to infect roots of plants that has been found in a 

 number of fungus parasites.^ 



/Of- 



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' ... % 





/o\ 



\ 



/2 



/■5 



/8 



30 



33 



36 



2/ 24 27 



■PiG. I. — Comparison of dry weights of tops, roots, and nodules of soybeans given in Table HI, grcwn 

 during November, December, and January. 



EFFECT OF SOIL TEMPERATURE UPON THE PRODUCTION OF NODULES AS 

 MEASURED BY DRY WEIGHTS 



Although it is clear that soil temperature does not, in most cases, 

 greatly modify the number of nodules produced, it was obvious from the 

 very beginning that the size to which they developed was markedly and 

 consistently affected. Such effect is shown graphically in Plate 2, where 

 nodules from an equal number of plants are shown placed in rows and in 

 Plate 3, where nodules from a larger number of plants are placed in tubes 

 of equal diameter. Dry weights of the nodules shown are given in Table 

 III. Data are given for the soybeans only for reasons already mentioned, 

 but, judging by visual evidence obtained in studying all four legumes 

 used, it is believed that all behaved in essentially the same manner. 



I Johnson. James, and Hartman. R. E., influence of soii, environment on the root-rot of 

 TOBACCO. /» Jour. Agr. Research. V. 17, no. 2, p. 41-86, pi. 1-8. 1919. Literature cited, p. 84-86. 



TiSDALE, W. H. RELATION OF TEMPERATtree TO THE GROWTH AND INFECTING POWER OF FUASRIUM 

 UNI. In Phytopathology, v. 7, no. s, p. 356-360, i fig., pi. u. 1917. 



