Acanthaceae
Mainly herbs, sometimes shrubs or vines. Lvs opposite, simple, exstipulate, often with cystoliths. Fls mostly in spikes, racemes, or dense heads (glomerules), occasionally solitary. Bracts often conspicuous and coloured. Calyx 4-5-lobed; lobes imbricate or valvate, occasionally much reduced. Corolla gamopetalous, zygomorphic, (1)-2-lipped; lobes convolute or imbricate in bud. Stamens 4 and didynamous, or 2, inserted on corolla. Ovary superior, sessile on a disc, 2-locular; ovules 2 or more per loculus. Fr. a capsule, mainly dehiscing from apex downwards; valves recurved and parting from central axis. Seeds mostly with indurated funicles which forcibly eject the seeds, usually non-endospermic.
c. 250 genera, 2500 spp., mainly tropical, but extending to warm temperate N. America and Eurasia.
A number of spp. in addition to the one described here are cultivated in N.Z. Some are amongst the commonest of our indoor plants, often being valued for their ornamental lvs and bracts. The most prominent genera grown outside, especially in warmer areas, are: Beloperone Nees, Jacobinia Moric., Justicia L., Strobilanthes Blume and Thunbergia Retz. Several spp. long-persist in gardens and may appear naturalised, in particular in Thunbergia, a genus of mostly climbing herbs and shrubs. Its spp. have opposite, generally hastate or sagittate lvs; fls solitary or racemose, with 2 large, foliaceous bracts; corolla large, funnelform or almost campanulate, with a curved or straight tube and a 5-lobed, scarcely bilabiate limb. The tropical and southern African Thunbergia alata Bojer, black-eyed Susan, is a perennial climbing herb with hairy stems and lvs, and bracts subtending the large, solitary, orange, black-centred fls. It sometimes seeds freely in gardens in the warmer parts of the North Id and grows rampantly almost to the point of being a nuisance.
