Abstract
Vincetoxicum phucanhense
(Apocynaceae, Asclepiadoideae), a new species from Vietnam, is described, illustrated, and compared with three morphologically similar species:
Vincetoxicum flexuosum
(R.Br.) Kuntze,
V. harmandii
(Costantin) Meve & Liede, and
V. tengii
(Tsiang) Meve & Liede.
V. phucanhense
differs from
V. flexuosum
in having shorter pedicels, very sparsely hairy sepal margins (vs. glabrous), a larger corolla, broadly elliptic pollinia (vs. globose), longer fruits, and longer seeds. It also differs from
V. harmandii
in having shorter petioles, smaller leaf blades, glabrous adaxial leaf surfaces (vs. hairy), and a larger corolla. In comparison with
V. tengii
,
V. phucanhense
can be distinguished by its larger corolla, corolla coloration (yellow, pink, or red vs. greenish), and broadly elliptic pollinia (vs. globose). A key to the 14 species of
Vincetoxicum
recorded in Vietnam is provided.