Columnea (Pentadenia) angustata
by Ron Myhr
Grown at Smithsonian Institution Greenhouses
The inflorescence of this species takes the form of an axillary cyme (branching flower stalk), which in part accounts for the large numbers of flowers produced in each leaf axil. This floral structure is characteristic of most gesneriads, but in other Columnea species the structure is usually reduced substantially so that flowers appear to be produced singly or in pairs. A closeup of a flower can be seen here and here, and another photo of a branch here.
A discussion of the axillary cyme can be found in the article Gesneriaceae: A Scientific Perspective in the chapter on Inflorescence Structure.