Acanthus L.

M. Thulin et al. Flora of Somalia Vol. 1-4 [updated 2008] https://plants.jstor.org/collection/FLOS

Morphology General Habit

Robust perennial herbs or shrubs

Morphology Leaves

Leaves pinnately lobed to divided, sometimes with pseudostipules

Morphology Reproductive morphology Flowers

Flowers in dense terminal spikes; bracts large, spinose-dentate; bracteoles lanceolate to linear

Morphology Reproductive morphology Flowers Calyx

Calyx 4-lobed; upper and lower lobes larger than the lateral ones

Morphology Reproductive morphology Flowers Corolla

Corolla 1-lipped (upper lip absent), 3-lobed; tube short

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens 4; filaments similar; anthers 1-celled, connate in pairs

Morphology Reproductive morphology Fruits

Fruit a capsule

Morphology Reproductive morphology Seeds

Seeds glabrous or puberulous.

Distribution

Some 30 species in tropical to warm temperate parts of the Old World.

Acanthaceae (part 1), Kaj Vollesen, Flora of Tropical East Africa, 2008

Morphology General Habit

Perennial herbs, shrubs or small trees; cystoliths absent.

Morphology Leaves

Leaves opposite or in whorls of 4, usually leathery with pale yellow thickened midrib, veins and margins, alternate pair if present usually much reduced, with sessile scale-like glands.

Morphology Reproductive morphology Flowers

Flowers in terminal or axillary racemoid cymes; bracts large, leathery, with 3 prominent longitudinal veins, with spinose margin or entire; bracteoles 2, filiform to ovate, spinose or entire. It is immediately recognisable by its large dark red flowers.

Morphology Reproductive morphology Flowers Calyx

Calyx divided to base into 4 glumaceous sepals which are thickened and horny at the base; dorsal sepal 1–3-veined, entire or with 2–3 small teeth, ventral 2-veined, entire or with 2 large triangular teeth or irregularly toothed, lateral 1-veined.

Morphology Reproductive morphology Flowers Corolla

Corolla tube short, white, thickened and spongy apically, with a dense band of thick retrorse hairs apically; limb split dorsally to give a 3–5-lobed lip, basally with a thickened callus, on both sides of and on callus with thick bulbous-based retrorse hairs; lobes broadly oblong, rounded or central emarginate.

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens 4, exserted, inserted just inside throat, two posterior held above anterior; two pair of filaments similar, curved, thick and bony, laterally compressed; anthers 1-thecous, oblong, with brushes of stiff hairs along whole length ventrally.

Morphology Reproductive morphology Flowers Gynoecium Ovary

Ovary 2-locular with 2 ovules per locule; style linear, glabrous; stigma of 2 lanceolate, acute lobes.

Morphology Reproductive morphology Fruits

Capsule 2–4-seeded, woody, ellipsoid, glossy, sessile, flattened dorsiventrally and rounded apically.

Morphology Reproductive morphology Seeds

Seed discoid, glabrous or sericeous-puberulous.

Distribution

Range: About 25 species from southern Europe to the Pacific and south through Africa to Angola, Zambia and Malawi.