Costus lucanusianus J.Braun & K.Schum.

Kamer 1, H. Maas-van de, Maas 1, P. J. M., Wieringa 1, J. J. & Specht, C. D., 2016, Monograph of African Costaceae, Blumea 61 (3), pp. 280-318 : 305-307

17. Costus lucanusianus J.Braun & K.Schum. — Fig. 4d ; Map 11

Costus lucanusianus J.Braun & K.Schum.(1889) 151; K.Schum.(1904) 392. — Type: Braun s.n. (holo B destroyed), Cameroon, South Province, Batanga.As the holotype was destroyed in Berlin and no other type material has been located we hereby select a neotype from a locality not far from the type locality: Van Andel et al. 3406 (neo WAG [ WAG0145874 ] ; isoneo KRIBI), Cameroon, South Province, Campo-Ma’an National Park , Ntem River , Ebianemeyong , at the foot of Asuangale falls, 350 m, 6 May 2001 .

Costus lucanusianus J.Braun & K.Schum. var. major K.Schum. (1904) 392, syn. nov. — Syntypes: Braun s.n. ( B destroyed), Cameroon, South Province, Gross-Batanga ; Zenker 1595 ( BM, E, G, K, L, LE, M, MO, P, S, WRSL) , Cameroon, South Province, Bipindi, 14 Dec. 1894 .

Costus dussii K.Schum. (1904) 402,f. 45B; Maas (1972) 121. — Type: Duss 2109b (holo B destroyed; lecto NY, selected by Maas 1972), Martinique, ‘Hauteurs du Carbet et Fonds Saint Denis’ .

Terrestrial herb, erect but in fruit often bending down, 1–5 m tall. Leaves many; sheaths 0.5–2 cm diam; ligule truncate to slightly 2-lobed, 1–4(–8) mm long, with a basal horizontal rim 1–2 mm high provided with a prominent row of needle-like hairs 2–6 mm long; petiole 4–10 mm long; sheaths, ligule and petiole rather densely to sparsely covered with erect hairs <1 mm long to glabrous; lamina narrowly elliptic, 12–33 by 3–10 cm, up- per side glabrous, lower side densely to sparsely covered with silvery, mainly erect hairs to c. 2 mm long to glabrous, base obtuse to cordate, apex acuminate (acumen 10–20 mm long), margin undulate. Inflorescence many-flowered, broadly ovoid to globose, 2–12 by 2–9 cm, sometimes elongating to c. 20 cm in fruit, terminating the leafy shoot; bracts, bracteoles, calyx, ovary and capsule glabrous or sparsely covered with erect and appressed hairs <1 mm long, calyx lobes often rather densely hairy, particularly along the margins. Flowers 2 per bract; bracts green, coriaceous, broadly to very broadly ovate-triangular, 1.5–3 by 1.5–3 cm, falling apart into separate fibers with age, callus inconspicuous, up to c. 2 mm long; appendages absent; bracteole boat-shaped, 17–20 mm long, callus 2–4 mm long; calyx 18–25 mm long, lobes broadly ovate-triangular to trian- gular, 4–12 mm long, horizontally spreading to reflexed, in fruit distinctly exceeding the bracts, callus sometimes present and then 2–3 mm long; corolla white, 30–45 mm long, glabrous, tube 10–15 mm long, lobes elliptic, 25–30 mm long; labellum at the outer side white with dark red upper part, inner side basally white with wide dark reddish margin and yellow to orange nectar guide, funnel-shaped, broadly obovate when spread out, 40–50 by 40–45 mm, margin crenate; stamen white, 30–35 by 10–15 mm, apex dark pink, anther 6–11 mm long. Capsule ellipsoid to broadly ellipsoid, 10–20 by 5–15 mm. Seeds 1–2 by 1–1.5 mm.

Distribution — North East Africa (Ethiopia, South Sudan); West Africa (Benin, Ghana, Guinea, Ivory Coast, Liberia, Ni- geria, Sierra Leone, Togo); Central Africa (Burundi, Cameroon, Central African Republic, Congo Brazzaville, Congo Kinshasa, Equatorial Guinea, Gabon, São Tomé & Principe); East Africa (Uganda); Southern Tropical Africa (Angola).

Habitat & Ecology — In savanna forest, secondary forest and swamp forest, in wet places along rivers and road sides, and in plantations, at elevations of 0–1700 m. Flowering and fruiting: all year through.

Field observations — Often plants are viviparous, the seedlings emerging from the ripe fruit. As the shoot with the heavy infructescence bends down and reaches the ground, the plantlets can start their life easily.

IUCN Conservation Status — Least Concern.

Notes — Costus lucanusianus can easily be recognized by having a row of distinct erect hairs on a horizontal rim at the base of a very short ligule. The flowers have horizontally spreading to reflexed calyx lobes. The labellum is completely white at the outer side contrasting with the inner side which has a dark red margin and dark yellow nectar guide. The lower side of the leaves is densely to sparsely covered with silvery hairs to glabrous. The apex of the stamen is pink and narrowly triangular. Boat-shaped bracteoles can be so compressed inside the inflorescence that they become 2-keeled. Costus lucanusianus is sometimes confused with C. afer . Costus lucanusianus is characterized, however, by a complete ring of hairs on the nodes, while in C. afer this ring is incomplete and less hairy. The lower side of the leaves is generally hairy in C. lucanusianus and glabrous in C. afer . The calyx lobes of C. lucanusianus are horizontally spreading to reflexed and those of C. afer are erect. The ligule in C. lucanusianus is 1–4 mm long vs 4–11 mm in C. afer . The bracts of C. lucanusianus are green, those of C. afer are reddish.

Figures

Map 11 Distribution of Costus lucanusianus J.Braun & K.Schum.

Fig. 4 Costus fenestralis Maas & H.Maas a. Habit showing few leaves in an apical rosette; b. detail of sheaths dilacerating into fibers; c. detail of withered bract; d. detail of bracteole and calyx; e. inflorescence (all: Jongkind et al. 5811, WAG). — Drawing by Hendrik Rypkema.