L., Sp. Pl. 639 (1753).
Derivation: Greek acantha, spiny; referring to the spiny leaf and bract margins of the type species A. mollis L.
Synonymy: Not Applicable
Common name: None
Shrubs without cystoliths, in introduced species the stem contracted and the leaves arranged in a basal rosette; leaves petiolate, lobed or irregularly dentate, sometimes spiny on margins, glabrous.
Flowers large, arranged in a spike at the apex of a scape (introduced species), subtended at their base by a bract and 2 bracteoles; calyx segments 4, the outer lower and upper segments larger than the 2 lateral ones; corolla with a short tube and a large shortly 3-lobed lower lip, lacking an upper lip; stamens 4, inserted at the top of the corolla tube in subequal pairs, exserted; filaments very thick, bony, curved, the lower pair of stamens twisted such that their anthers are pressed against the anthers of the upper pair; anthers 1-celled, bearded along sutures and often on the dorsal surface; ovary with 2 superposed ovules per cell; style of similar length to the stamens; stigma 2-lobed.
Capsule ovoid-oblong, glabrous, leathery, with 2-4 seeds borne upon strong hooks; seeds large, glabrous, in introduced species with a smooth surface.
8-10 species of which half (subgenus Acanthus) occur in the forests of Europe and Africa. The rest are mangrove species belonging to subgenus Dilivaria and occur in coastal localities from India to Polynesia including northern Australia.
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