Isoglossa milanjiensis S.Moore

Flora Zambesiaca Acanthaceae (part 2) by Iain Darbyshire, Kaj Vollesen and Ensermu Kelbessa

Morphology General Habit

Scrambling perennial herb or subshrub (15)100–350 cm tall.

Morphology Stem

Stems retrorse-pubescent in two opposite lines and at nodes, later glabrescent.

Morphology Leaves

Leaves ovate or elliptic, 8–14.5(19.5) × 2.8–6(10) cm, base attenuate, apex acuminate, margin and principal veins pubescent or sparsely so, often also with scattered hairs on upper surface, midrib pilose towards leaf base when young, hairs extending onto young petioles; lateral veins 6–10 pairs; petiole 30–65 mm long.

Morphology Reproductive morphology Inflorescences

Inflorescence terminal, spiciform or often with 1–6 lateral branches at maturity, sometimes with secondary branching and forming a ± pyramidal panicle 4–15 cm long, cymules dense in upper portion of axis, more widely spaced below, sessile, single-flowered or one bract of a pair sometimes sterile on lateral branches; axis pale-pubescent, hairs retrorse towards base of spike, antrorse upwards, sometimes also glandular-pubescent; cymule bracts flabellate, elliptic or suborbicular in lower portion of axis, then 4–11 × 2–6.5 mm, becoming narrowly elliptic or lanceolate in upper portion, then 3–6 × 1–2.5 mm, base attenuate, apex acuminate, attenuate or acute, margin and often midrib ciliate, surfaces largely glabrous or sparsely to densely glandular-pubescent; bracts subtending inflorescence branches usually larger and ovate; bracteoles lanceolate, 3–6.5 × 1 mm.

Morphology Reproductive morphology Flowers Calyx

Calyx lobes lanceolate, 4.5–7.5 mm long in flower, 7.5–11 mm in fruit, indumentum as bracts.

Morphology Reproductive morphology Flowers Corolla

Corolla (12)13–16 mm long, white or tinged reddish, palate often with conspicuous purple to red-brown markings; limb sparsely puberulous externally; tube 3.7–5 mm long, somewhat widened upwards, with an interrupted ring of short hairs at attachment point of stamens within; upper lip oblong, hooded, (7.5)8.5–11.5 mm long, lobes 0.7–1.8 mm; lower lip (8)8.5–12 mm long, lobes rounded, 1–2.5 mm, palate upraised with prominent herring-bone patterning.

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens attached in upper half of corolla tube; filaments free for 4–5 mm; anther thecae superposed, strongly oblique, at least lower theca held almost patent to filament, upper theca 1.35–1.7 mm long, lower theca 1.25–1.6 mm long.

Morphology Reproductive morphology Fruits

Capsule 10–14 mm long, glabrous.

Morphology Reproductive morphology Seeds

Seeds 3.5–4 × 2.8–3.5 mm, rugose when immature, inconspicuously so at maturity.

Distribution

Not known elsewhere.

Ecology

Submontane and montane forest including margins and clearings, exposed riverbanks, mature Cupressus plantations, often dominant in forest understorey; (350)900–2000 m.

Conservation

Conservation notes: Only known from Mts Mulanje, Gorongosa and mountains along the Zimbabwe–Mozambique border where it can be locally abundant, although some populations have been lost to forest clearance at lower altitudes. With only 9 locations known and inferred threats, considered Vulnerable under IUCN criterion B.