Coleus prittwitzii (Perkins) A.J.Paton

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. Pycnostachys, G Bramleyshaped. Flora of Tropical East Africa. 2009

Type

Type: Tanzania, Iringa District: Ndembera flood plain, near Gominyi, Prittwitz 28 (B†, holo. K!, fragment)

Morphology General Habit

Perennial herb, 1.5–3 m tall, becoming woody below

Morphology Stem

Stems arising from a woody rootstock, erect, branching, quadrangular, or rounded-quadrangular where woodier, pubescent with short eglandular closely appressed hairs giving a silvery appearance, and with clear sessile glands

Morphology Leaves

Leaves opposite or whorled in 3s or 4s, sessile; blades oblanceolate, 3–7.5 × 0.3–1.6 cm, margins with upward pointing serrations in the upper half, apex shortly acuminate, base sessile, densely pubescent with short appressed eglandular hairs, these particularly dense on the margins and on the venation beneath giving a silvery appearance; venation appearing ± parallel (secondary vein pairs at ± the same angle as at the midrib)

Morphology Reproductive morphology Inflorescences

Inflorescence dense, when in flower forming a narrowly conical shape, in fruit 55–100 × 16–18 mm; bracts subtending entire inflorescence lanceolate, 10–15 mm long, acuminate, enclosing buds then becoming deflexed in flower, densely pubescent with short eglandular hairs, persistent through flowering stage; bracts subtending single flowers forming a conspicuous coma at the tip of the inflorescence, lanceolate with a long acuminate apex that curls over, 5–11 mm long, chartaceous, pubescent with short eglandular hairs, ciliate

Morphology Reproductive morphology Flowers Calyx

Calyx dull purple to pale brown, with tube ± 1 mm long at anthesis, outer surface with eglandular hairs and scattered yellow sessile glands, inner surface with 0.5 mm triangular scales between calyx lobes; lobes 5, subulate, slightly curved, with a membranous wing either side of the midrib, ± subequal, 3–4 mm long, pubescent with fine eglandular hairs; fruiting calyx with tube 4–4.5 mm long, strongly compressed dorsally, ventrally gibbous, lobes erect, lengthening to 5–6 mm

Morphology Reproductive morphology Flowers Corolla

Corolla french to pale to azure blue, ± 10 mm long; tube pubescent with eglandular hairs, also with yellow sessile glands, very narrow and parallel-sided for ± 4 mm, then curving sharply downwards and broadening for ± 3 mm before opening out into two lips; posterior lip shorter than anterior, ± 3 mm long, the backs of the lobes densely pubescent, with yellow and red sessile glands; anterior lip ± 4 mm long, ± 2 mm deep, densely pubescent, with red sessile glands on the front of lip

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens connate for ± 2 mm, barely exserted

Morphology Reproductive morphology Fruits

Nutlets (immature) ± 1 mm long.

Ecology

Wet or swampy grassland; 1500–2100 m

Conservation

Known only from a relatively small part of Tanzania and northern Zambia and the habitat under some threat from expanding habitation; possibly threatened.

Note

Pycnostachys prittwitzii can be recognised by its attractive oblanceolate leaves, which have a silvery appearance due to the closely appressed white indumentum, and its bracts, which are acuminate at the apex and form a coma at the tip of the inflorescence. The venation isalso distinctive as it is ± parallel and the leaves are generally ternate. All these features distinguish P. prittwitzii from P. niamniamensis, a closely related species. P. niamniamensis has elliptic or narrowly elliptic leaves, the venation is less conspicuous and it also has a shorter calyx tube in flower, and longer calyx lobes in fruit, and its bracts do not form a coma at the tip of the inflorescence. There is a group of specimens from northern Zambia that have anomalously large inflorescences, but in all other respects match the more typical P. prittwitzii (e.g. Richards 22339).

Distribution

Range: Zambia Flora districts: T4 T7