238 



Plant Physiology 



times no plant structures have, perhaps, attracted more 

 attention than the nodules, or tubercles, of the leguminous 



FIG. 61. Infection thread and abnormal tissue in a tubercle developing 

 upon the root of Vicia saliva. At the right, infection thread in root- 

 hair. [After Geo. F. Atkinson.] 



plants. These structures are abnormal growths resulting 

 from the attacks of parasitic bacteria, Figures 60 and 61. 



