Pogostemon aquaticus (C.H.Wright) Press

Lamiaceae (Labiatae), A.J. Paton, G. Bramley, O. Ryding, R.M. Polhill, Y.B. Harvey, M. Iwarsson, F. Willis, P.B. Phillipson, K. Balkwill, C.W. Lukhoba, D.F. Otieno, & R.M. Harley. Pogostemon, R.M. Polhill. Flora of Tropical East Africa. 2009

Type

Type: Mozambique, Unango [Unangu], to Lake Chilwa [Shirwa], W.P. Johnson 15 (K!, holo.)

Morphology General Habit

Aquatic perennial herb.

Vegetative Multiplication Rhizomes

Rhizomes creeping, rooting at the knobbly nodes

Morphology Stem

Stems sometimes purple basally, spongy, terete, hollow, to 60 cm or trailing in water before ascending and up to 1.2 m, producing relatively short flowering branches from upper nodes, with long hairs around the nodes, otherwise glabrous

Morphology Leaves

Leaves in whorls of (3–)5, linear to very narrowly linear-elliptic, 5–20 × 0.5–1.3 cm, but submerged leaves sometimes strap-shaped and up to 30 cm or more long, dentate to subentire under water, tapered to an acute tip, attenuate at base, glabrous except for small hairs on midvein above and longer ones at the base; lateral veins ascending and rather prominent beneath

Morphology Reproductive morphology Inflorescences

Inflorescence terminal, with very many small flowers, 3–10 cm long, congested, columnar, sessile or occasionally interrupted above first verticil, the verticils otherwise scarcely evident but ± 15–20, each with up to 40 flowers; bracts linear to very narrowly linear-elliptic, 2–5 mm long, conspicuously ciliate but almost glabrous on surfaces; bracteoles linear and distinctly smaller

Morphology Reproductive morphology Flowers Calyx

Calyx 1.5–2(–3 in fruit) mm long, with ciliate lobes, shortly pubescent outside and on lobes inside; lobes subequal, ovate-triangular, 0.4–0.7(–1 in fruit) mm long

Morphology Reproductive morphology Flowers Corolla

Corolla white with pink, lilac or mauve lobes, 2.5–3 mm long; tube only slightly exserted from calyx; lobes subequal, elliptic-obovate, the anterior one sometimes rather more triangular, 0.7–1 mm long, ciliate and slightly pubescent

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens exserted, subequal; filaments 3–4 mm long, conspicuously hairy at the middle; anthers 0.2–0.3 mm long

Morphology Reproductive morphology Flowers Gynoecium Style

Style 4.5–5 mm long

Morphology Reproductive morphology Fruits

Nutlets dark glossy brown, ovoid-ellipsoid, 0.7–0.9 × 0.6–0.7 mm

Figures

Fig 6, p 31

Ecology

Streams; 1700 m

Conservation

Collected only once in East Africa, but quite widely distributed in neighbouring countries and probably not threatened.

Distribution

Range: Zambia, Malawi, Mozambique Flora districts: T4