Costus dinklagei K.Schum. — Plate

Maas-van de Kamer, H., Maas, P. J. M., Wieringa, J. J. & Specht, C. D., 2016, Monograph of African Costaceae, Blumea 61 (3), pp. 280-318 : 294-295

5. Costus dinklagei K.Schum. — Plate 1d; Map 4

Costus dinklagei K.Schum. (1904) 408. — Type : Dinklage 987 (holo B destroyed), Cameroon, South Province , Gross-Batanga. As the holotype at Berlin was destroyed and no other original material has been located, we hereby select a neotype from a locality not far from the type locality: Van Andel et al.3549 (neo WAG 2 sheets [WAG0146035,WAG0380166];isoneo KRIBI, SCA, U [U0064546], WAG-spirit [WAG0028342], YA), Cameroon, South Province, Mont d’Ėléphant,road Bidou-Akom II, foot of the hill, 23 m, 10 June 2001.

Terrestrial herb 1–3 m tall. Leaves many; sheaths 0.5–2.5(–3) cm diam; ligule chartaceous, truncate, 10–20 mm long; petiole 3–10 mm long; sheaths, ligule and petiole hairy as the lower side of the leaves; lamina narrowly elliptic, sometimes narrowly obovate, 15–40 by 5–13 cm, upper side glabrous, lower side densely to sparsely covered with erect to appressed brown hairs 0.5–2 mm long, base acute, apex acuminate (acumen 15–40 mm long). Inflorescence many-flowered, ovoid to ellipsoid, 4–15 by 2.5–6 cm, terminating a separate leafless shoot 5–30 cm long, rarely terminating a leafy shoot; bracts, bracteoles, calyx, ovary and capsule densely covered with erect hairs <1 mm long. Flowers 1 per bract; bracts green to dark green, sometimes reddish, coriaceous, broadly ovate-elliptic, 1.5–5.5 by 1–3.5 cm, callus 1–2 mm long; appendages absent; bracteole boat-shaped, 16–35 mm long, callus 3–4 mm long; calyx 12–20 mm long, lobes shallowly to broadly ovate-triangular, 2–6 mm long, callus 1–2 mm long; corolla hyaline, white to pale pinkish, 45–55 mm long, glabrous, tube 15–20 mm long, lobes narrowly elliptic, 30–40 mm long; labellum at the outer side white to (pale)pink, inner side white to pink with darker coloured margin and often pale yellow nectar guide, funnel-shaped, broadly obovate when spread out, 40–60 by 30–50 mm, margin crenate or undulate, fimbriate; stamen white, 20–35 by 10–13 mm, apex pink, anther 6–7 mm long. Capsule not seen. Seeds c. 2 by 1 mm.

Distribution — West Africa ( Nigeria); Central Africa ( Cameroon, Equatorial Guinea, Gabon).

Habitat & Ecology — In rainforest, often near streams or in wet places, on clay soil, at elevations of 0–1100 m. Flowering and fruiting: from March to July and in December.

IUCN Conservation Status — Near Threatened.

Notes — Costus dinklagei can be recognized by its inflorescence terminating a separate leafless shoot with 1-flowered bracts and hyaline whitish erect corolla lobes. The labellum is white to pale pink with yellow nectar guide, basally funnel-shaped but with the upper part horizontally flattened. The lower side of the leaf lamina, the sheaths and the petioles are hairy. The apex of the stamen of C. dinklagei is narrowly triangular ( Hallé 1967).

Costus dinklagei can be confused with C. dubius both having a basal inflorescence with green, unappendaged bracts, but C. dinklagei has hyaline, whitish corolla lobes and a white to pale pink labellum with yellow nectar guide and dark pink margin, whereas in C. dubius the white corolla lobes are not hyaline and the labellum is white with only a yellow nectar guide. Moreover, in C. dinklagei the lower side of the lamina, the petioles and the sheaths are distinctly hairy, while all vegetative parts are glabrous in C. dubius .