COMPOUND ORGANISMS 195 



bacteria-like organisms to which the name of 

 Bacillus radicola has been given. 



The root becomes infected by this bacillus 



Fig. 22. Root tubercles on the roots of the Kidney- 

 bean plant. 



from the soil, in ordinary samples of which 

 it is apparently always present. The bacillus 

 enters through a root-hair, and when it reaches 

 the interior of the cortex it multiplies there, 



