Steps in the development of root nodules:
1. Rhizobium bacteria contact a susceptible root hair, divide near it.
2. Upon successful infection of the root hair cause it to curl
3. Infected thread carries the bacteria to the inner cortex. The bacteria get modified into rod-shaped bacteriodes and cause inner cortical and pericycle cells to divide. Division and growth of cortical and pericycle cells lead to nodule formation.
4. A mature nodule is complete with vascular tissues continuous with those of the root.
