The stem may be well developed, bearing leaves at marked intervals (caulescent habit), or short to acaulescent with contracted internodes and ± densely aggregated leaves. In the latter group a distinction can be made between proper rosette plants such as Saintpaulia (now included in Streptocarpus, Nishii et al. 2015), with the (usually spirally arranged) leaves forming a dense, ± plain, basal rosette, and “rosulate” plants such as Codonobea with rather loosely tufted leaves. The stem may be thick or thin, woody or herbaceous, erect or creeping, branched or unbranched. See Leaf Form and Arrangement for a full discussion, as well as Life Forms and Growth Patterns for further discussion.
The root system consists of the primary root (developing from the radicle of the seedling), and lateral roots emerging from the basal (usually underground) parts of the stem. Unlike most other dicotyledons, the primary root never seems to occupy a dominant position and is of subordinate functional importance. Developmental delay to complete suppression of the primary root is observed in some Old World Gesneriaceae (Streptocarpus spp., Rhynchoglossum).
For a discussion of root structures adapted to different life cycles and environmental circumstances, see Life Forms and Growth Patterns I.