These are Sinningia tubers. The popular mini-Sinningias are members of this group. This group of plants also has a type of underground storage mechanism. Rhizomes form along the roots and are renewed each growing season. Rhizomes have overlapping scales that resemble those of a pine cone.
Most rhizomatous gesneriads have a dormant period, just like their tuberous relatives.
Rhizomes can also form above the soil level. These are called propagules. This illustration shows a Kohleria rhizome. Most gesneriads fall into this classification. Although the above two groups have fibrous roots in addition to tubers or rhizomes, this group lacks any type of storage organs.