Annual below-ground tubers on distal part of plagiotropic above-ground stems. The tubers serve as storage organs and have a bud bank. The tuber is formed on a stem in autumn when the plagiotropic above-ground stem penetrates into soil and transforms. One or several apical internodes thicken, food reserves are deposited in the swollen part of the stem. The plagiotropic stem provides a connection to the mother plant. It may bear green leaves and roots and decays completely after the tuber is formed. This type ensures a fast vegetative spreading, high mobility in space and a short persistence at a particular site

[other examples: Calystegia silvatica, Rubus caesius, Rubus fruticosus agg.].

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