Argyreia nervosa (Burm.f.) Bojer

Global description

Argyreia nervosa is a large herbaceous vine, vivacious with a more or less woody base. Stems and leaves (especially the bottom) are densely woolly, giving them a silvery color. The simple alternate leaves are broadly oval, cordate at the base and acuminate at the apex. The venations are clearly visible and projecting on the underside. The inflorescence is an axillary cyme, with long stalk, topped by a group of 3 to 6 shortly stalked flowers. The five sepals are covered on the external surface with a white tomentum and are nearly smooth on the inside. Corolla is campanulate, and consists of five fused petals forming a flared funnel at the top, 6 cm long. It is white on the outside and dark purple inside, lighter on the edge. The fruit is a globular indehiscent capsule, yellowish in colour, containing 4 brownish seeds more or less trigonal.

General habit

Argyreia nervosa is a great twining vine, vivacious, herbaceous, with a more or less woody base. It measures up to 10 m in length. It wraps around any support and quickly becomes invasive.

Underground system

The plant has a taproot system.

Stem

The stem is cylindrical, solid, woody at the basal part. It can measure up to 6 cm in diameter at the base. It is covered with abundant white tomentum which gives it a silvery color, becoming more or less tawny in the older parts.

Leaf

The leaves are simple, alternate, long-stalked. The petiole can reach 8 to 15 cm long, it is abundantly tomentose. The blade is broadly oval to orbicular, 15 to 30 cm long and 10 to 22 cm wide. The base is cordate, the apex wedged or acuminate and margin entire. The underside is covered with abundant white tomentum while the upper face is sub-glabrous and murky green. A waxy coating holds the two halves of the leaves glued in aestivation. The Midrib and the 11 to 16 pairs of lateral ribs are clearly protruding on the underside.

Inflorescence

The inflorescence is an axillary cyme, held by a long tomentose peduncle (up to 20 cm). At the top of the peduncle, the flowers are grouped by 3 to 6, each carried by a short peduncle (0.7 to 1.5 cm). At the base of the flowers are deciduous bracts, oval, elliptical, embossed, narrowly acuminate at the top, 3.5 to 6 cm long.

Flower

The calyx is formed by 5 sepals, slightly unequal, elliptical and sub circular, 1.5 cm long. They are covered with a white tomentum on the outside and almost glabrous inside. The campanulate corolla is formed of five petals, fused into a long tube of 5 to 7 cm, flaring at the top in a funnel, 7 to 8 cm in diameter. The exterior is white and pubescent along the tube and between the folds, especially on the middle part of the lobes, while the interior is dark purple, clearing to the top of the petals. The five stamens are included in the corolla tube, as well as the style. The stigma is capitate, divided into two tuberculate masses.

Fruit

The fruit is an indehiscent capsule, ovoid to orbicular, yellowish to brownish. It measures 1 to 2 cm in diameter and contains a farinaceous pulp. It consists of 4 loculus each containing a seed.

Seed

The seed is more or less trigonal and rounded on the back, 6 to 10 mm long and 6 to 7 mm in diameter. It is brownish in colour with pubescent hilum.

https://www.gbif.org/species/2928692