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Aeschynomene americana

Family

Fabaceae

Botanical Name

Aeschynomene americana L.

Linnaeus, C. von (1753) Species Plantarum: 713. Type: Lecto: Jamaica, B. W. I., Sloane. Fide V. E. Rudd, Contr. U.S. Nat. Herb. 32 (1955) 23-30.

Common name

American Jointvetch

Weed

*

Stem

Flowers and fruits as a herb or a shrub about 1-2 m tall.

Leaves

Stipules +/- peltate, about 10-13 mm long, narrow, margins clothed in hairs, two-branched, longitudinally veined. Each compound leaf with 50-60 leaflets. Compound leaf axis clothed in long hairs, axes ending in a short point. Leaflets sessile, (or almost sessile) blades about 6-12 x 1-2 mm, margins hairy, with a small tooth on one side. Venation longitudinal and parallel with 3-5 longitudinal veins.

Flowers

Each flower subtended by two hairy, lanceolate bracts each about 2-2.5 mm long. Calyx 4-4.5 mm long, lobes 2. Petals clawed, i.e. stalked. Stamens 10, filaments all fused to form a tube open on one side. Filament about 4 mm long, attached close to the base of the anthers. Pollen orange. Ovules 6-10 in each ovary.

Fruit

Fruits about 2.5-3 cm long, clothed in simple, erect hairs. Fruits consist of a string of 2-8 segments each containing one seed. Segments attached on one side of a 'bean string' and breaking off as one-seeded nuts. Seeds glossy brown, about 3 x 2 mm. Embryo about 1.4-2 mm long. Cotyledons about 1.5 mm long. Radicle about 0.75 mm long.

Seedlings

Cotyledons ovate to elliptic, about 7 x 5 mm. Petioles less than 1 mm long. First pair of leaves compound with 13-20 leaflets, each leaflet about 4-6 mm long. At the tenth leaf stage: leaf compound with about 50-60 closely-spaced leaflets. Leaflets linear, about 10-15 x 2-3 mm. Leaflet margin with several hair-like teeth near the apex. Compound leaf petiole distinctly kinked about halfway along its length. Stipules hairs, medifixed with a total length about 15 mm, Each arm about 5-8 x 2 mm.

Distribution and Ecology

An introduced species originally from Jamaica now naturalized in NT, CYP and NEQ. Altitudinal range not known but at present extends from near sea level to 850 m. Also naturalized n Malesia and the Pacific islands.

NT

X

CYP

X

NEQ

X

Herb (herbaceous or woody, under 1 m tall)

X

Shrub (woody or herbaceous, 1-6 m tall)

X

RFK Code

3554