Unlike other bulb types, far from being an underground stem base, this is a thick root
While the other bulb types are specialized stems, a tuberous root is a true root, thickened to store nutrients. Fibrous roots for uptake of water and nutrients grow from its sides and tip. Tuberous roots grow in a cluster, with the swollen tuberous portions radiating out from a central point. The growth buds are at the bases of old stems rather than on the roots themselves. Dahlia and daylily (Hemerocallis) are well-known examples of plants with tuberous roots.
If it has a growth bud, an individual tuberous root can give rise to a separate, new plant.