Description from Flora of China
Skinneria Choisy; Spiranthera Bojer.
Herbs or shrubs, often twining, sometimes prostrate. Leaves usually petiolate, rarely sessile, margin entire, dentate, or palmately or pedately lobed or compound. Flowers axillary, solitary or in few- to many-flowered, variously branched cymose inflorescences; bracts usually small. Sepals variable in shape, often convex, subequal or outer 2 smaller, persistent, often enlarged in fruit. Corolla often yellow or white, sometimes with a darker center, funnelform or campanulate, usually glabrous, or midpetaline bands ± sericeous, sometimes only at apex; limb entire or ± 5-angled. Stamens included, often unequal; anthers often spirally twisted; filaments dilated basally, filiform distally; pollen 3-12-colpate or polyrugate, not spiny. Disc ringlike. Pistil included; ovary (imperfectly 2-)4-loculed, 4-ovuled. Style 1, filiform; stigmas 2-globular. Capsule 1-4-loculed, usually 4-valved or ± irregularly dehiscing. Seeds 4 or fewer, glabrous or pubescent to villous especially at margin.
Approximately 80 species: tropical regions of Africa, Asia, Australia, North and South America; 19 species in China.
The generic name Merremia was published as a nomen nudum by Dennstedt (Schlüssel Hortus Malab. 12, 23, 34. 1818). Several modern floras attribute the valid publication of the
name to H. Hallier (Bot. Jahrb. Syst. 16: 581. 1893), but Endlicher (1841) actually validated the name.
Merremia is often confused with Ipomoea, which has pantoporate, spiny pollen, straight anthers and very few species with yellow corollas. It is also confused with Operculina, which
consistently has a fruit with a circumscissile lid that detaches first, leaving a fragile endocarp that shatters irregularly. The distribution of hairs on the corolla is taxonomically important
in Merremia; this is most easily discerned on mature flower buds.