Tridynamia

Accepted name/Authority/Place of publication:

TRIDYNAMIA Gagnep., Notul. Syst. (Paris) 14: 26. 1950.

Tribe:

Cardiochlamyeae

Synonyms:

Porana Burm.f., p.p., sensu

Type Species:

Tridynamia eberhardtii Gagnep. (= T.megalantha (Merr.) Staples)

Habit:

Lianas, lower stem woody, glabrescent, upper branches herbaceous, ± tomentose-villose.

Leaves:

Leaf blade cordiform, stiffly chartaceous or subcoriaceous, densely pubescent abaxially; venation pedate basally, secondary veins 2 or 3 basal pairs and 1, 2 or 3 alternate veins above, veins prominulous abaxially; petiole terete or compressed, sulcate adaxially, pulvinate.

Inflorescences:

Inflorescence axillary (or terminal), bracteose, racemose or paniculate, flowers fascicled (rarely solitary) at nodes, anthesis proceeding acropetally; bracts foliaceous, shape, texture, indumentum, and venation like the leaves; bracteoles 3, unequal, attached just below calyx, scale-like or bracteose, persisting in fruit.

Flowers:

Flowers showy, fascicled; sepals free, quincuncial, odorless or fragrant; corolla white, pale yellowish, or blue-violet, campanulate to broadly funnelform, 1–3.5(–5.5) cm; limb entire to vaguely 5-lobed, smooth or jagged, outside pubescent apically, inside glabrous; stamens included or exserted; filaments basally pilose or glabrous; anthers sagittate, versatile; pollen 3-colpate, not spiny; pistil included or exserted, disc 5-lobulate or absent. Pistil included or exserted; disc 5-lobulate or absent; ovary unilocular, ovules (2 or) 4; style 1, thread-like; stigma entire or 2-lobed, wrinkled.

Pollen:

Pollen 3-colpate, not spiny.

Fruits:

Fruit an indehiscent utricle, ovoid, ellipsoid, or obovoid, often apiculate by indurate style base, papery, wrinkled, glabrous or pilose-tomentose, tightly enclosed in accrescent, papery calyx; outer 2 or 3 sepals greatly enlarged, basally enclosing utricle, flat and slightly flaring above, with usually 9 (7–11) longitudinal veins basally, veins prominent abaxially; inner sepals slightly enlarged.

Seeds:

Seed 1, shaped like utricle, reddish-brown to black, smooth, glabrous; hilum basal, circular.

Distribution:

Northeastern India and the Andaman Islands across southeastern Asia to southern China and Hainan Island. map

Number of Species:

Infrageneric Characters:

The characters diagnostic for Tridynamia are: the suffrutescent habit; 3 sepaloid bracteoles; unequal sepals; showy, campanulate or broadly funnelform corolla; sagittate, versatile anthers; unequally accrescent fruiting calyx with the outer 2 or 3 sepals greatly enlarged, oblong-linear, and the inner sepals only slightly enlarged; fruiting sepals with 7 or 9 parallel longitudinal veins at the base, with 3 reaching the apex.
The genus Tridynamia comprises two species pairs. Tridynamia bialata and T. sinensis share the features of bluish corolla and outer 2 sepals greatly enlarged in fruit; T. megalantha and T. spectabilis share the characters of white corolla and the outer 3 sepals greatly enlarged in fruit.

References:

Gagnep., Notul. Syst. (Paris) 14: 26. 1950

Ooststroom, S.J. van. Blumea 12: 39-40. 1963.

Staples, Novon 3: 33. 1993

R.C. Fang & G. Staples in C.Y. Wu & P.H. Raven, Fl. China 16: 281. 1995

G. Staples, 2010. Flora of Thailand Convolvulaceae 10(3): 462-463.