Information about the underground parts of plants is currently scattered in different parts of the plant entries. Rhizome is listed under Plant Habit, Corm and Stolons/Runners are listed under Propagation: Other methods, and Bulb is listed in both places. I've often wished that the various underground structures of plants (rhizomes, tubers, taproots, bulbs, corms, etc.) were all listed together in their own category.