Petalidium Nees

J. R. Timberlake, E. S. Martins (2013). Flora Zambesiaca, Vol 8 (5) Acanthaceae Part 1. Royal Botanic Gardens, Kew

Morphology General Habit

Perennial herbs, subshrubs or shrubs; cystoliths conspicuous; stems quadrangular to rounded

Morphology Leaves

Leaves opposite, entire or toothed

Morphology Reproductive morphology Flowers

Flowers axillary and solitary or in racemes or (outside Flora area) in large contracted inflorescences; bracts rudimentary to well-developed; bracteoles large and conspicuous, often leathery and reticulately veined, enclosing calyx and corolla tube

Morphology Reproductive morphology Flowers Calyx

Calyx divided almost to base into 5 segments or 2 lower lobes ± fused; lobes subequal or dorsal slightly wider

Morphology Reproductive morphology Flowers Corolla

Corolla contorted in bud, puberulous on outside; tube straight or curved, widening into a distinct throat, palate prominently transversely ribbed and with stiff retrorse hairs (sometimes all lobes with hairs); lobes subequal, spreading

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens 4, didynamous, inserted dorsally in throat, tube and base of filaments hairy at point of insertion, each long and short filament fused at base and fused part running like hairy ridges into tube; anthers 2-thecous, thecae oblong, subequal, rounded apex, with short spurs at base

Morphology Reproductive morphology Flowers Gynoecium Ovary

Ovary 2-locular, 4-ovulate or 2 lower abortive; style glabrous or hairy; stigma lobes linear, flattened, unequal or subequal-Capsule 2–4-seeded, ovoid, with thickened apical 'knob', glossy, glabrous or puberulous; placentae at maturity separating elastically from walls from base upwards; retinaculae strong, hooked

Morphology Reproductive morphology Seeds

Seeds discoid, densely covered with hygroscopic hairs.

Distribution

A genus of 35–40 species, mostly in Angola and Namibia; one species in India. The genus is in need of monographic work.