254 AGEICULTUEAL AND INDUSTRIAL BACTEEIOLOGY 



of stimulating the meristematie cells to increased rapidity 

 of development. In consequence a small tumor or mass of 



Pig. 58. — Nodules on roots of a leguminous plant. 



cells develops rapidly and protrudes from the main portion 

 of the root as a nodule. This nodule may be regarded as a 

 modified rootlet. 



