Aeschynanthus siphonanthus

Photo by Christian Feuillet
Grown Royal Botanic Garden, Edinburgh

A number of Aeschynanthus species, such as A. lobbianus and A. pulcher have tube-like calyces.  A. siphonanthus is distinguished by the lime green color of the calyx.  Note the emerging buds, reminiscent of lipstick emerging from a tube -- hence the common name of "Lipstick Plant" for some species of Aeschynanthus.