Costus spectabilis (Fenzl) 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 : 310-311

22. Costus spectabilis (Fenzl) K.Schum. — Plate 4c ; Map 13

Costus spectabilis (Fenzl) K.Schum. (1892) 422; (1904) 421. — Cadalvena spectabilis Fenzl (1865) 140. — Kaempferia spectabilis (Fenzl) Baker (1898) 297. — Type: Boriani s.n. (holo W destroyed), Sudan, Fazughli (‘in Aethiopiae terra Fassoglu’). The following collection is selected here as neotype: Schweinfurth 1345 (neo BM,designated here; isoneo G, K, L, P), Sudan, Gallabat (‘Am linken Ufer der Gendua’), June 1865. A drawing in the B herbarium with annotation: ‘ 18 Juni 1865, Ethiopia, in Gallabas , an der Gendua’ is probably made of Schweinfurth 1345, the present neotype of this species .

Costus pistiifolius K.Schum.(1892) 424. — Cadalvena pistiifolia (K.Schum.) Baker (1898) 297. — Type: Von Mechow 315 (holo B destroyed; lecto Z, designated here), Angola, Prov. Malanje, Malanje (‘Malandsche’), Oct. 1879 .

Cadalvena dalzielii C.H.Wright (1912) 195; C.H.Wright (1915) t. 3013, syn. nov. — Type: Dalziel 229 (lecto K, designated here), Nigeria, Yola Prov- ince, Kilba Country, 30 July 1909; other syntype: Dalziel 560 ( K 2 sheets, E 2 sheets), Nigeria, South of Sokota Province and throughout Kontagora Province, 12 June 1911 .

Terrestrial shootless rosulate herb to c. 0.1 m tall; rhizomes vertically directed, to c. 18 cm deep; horizontal runners to 5–20 cm long, (1–) 3–9 mm diam, both rhizomes and runners covered with brownish, imbricate, membranous sheaths; roots with side roots up to c. 10 cm long. Leaves 4 per shoot, forming a funnel when young, later spreading horizontally and forming a rosette of partly overlapping leaves flat on the ground; ligule and petiole absent; lamina bright yellowish green above, paler green with reddish venation to completely reddish below, often with (dark) reddish margins 0.5–1 mm wide, definitively thick- ened and fleshy, imbricate, broadly obovate to broadly elliptic to suborbicular, 4–15(–17) by 4–17 cm, upper side glabrous, lower side densely covered with soft, erect hairs <1 mm long, margin ciliate, base attenuate, extreme base of leaf fleshy to c. 5 mm thick and 10–35 mm long, at an angle of 90° with the lamina surrounding the inflorescence, apex obtuse and often mucronate. Inflorescence terminal, formed in the centre of the rosette, up to 17-flowered, basally enclosed by the more or less overlapping fleshy extreme base of the leaf laminas and by the uppermost 4–5 (whitish and fleshy) sheaths; sheaths 2–4 by 1.5–3.5 cm, apex rounded, upper part reflexed with a horizontal rim of 0.7–0.8 cm high, together forming a cup of 0.8–2.5 cm diam around the inflorescence; the uppermost sheaths, outer side of bracts, bracteoles, calyx and apex of ovary densely to sparsely covered with soft, erect hairs <1 mm long to glabrous, capsule glabrous. Flowers 1 per bract, erect; bracts reddish, membranous, narrowly triangular, 1.7–3.2 by 0.6–0.8 cm, callus yellow, inconspicuous; appendages absent; bracteole boat-shaped, 8–25 mm long, callus absent; calyx reddish, green, or purple, 15–30 mm long, split on one side, lobes 2, narrowly triangular, c. 1 mm long, callus inconspicuous; corolla hyaline, pale yellow to pale orange, 40–100 mm long, glabrous, tube 20–45 mm long, lobes narrowly ovate-triangular, 20–55 mm long; labellum dark yellow to orange, horizontally flattened, obtriangular to obovate to suborbicular when spread out, 50–70 by 30–50 mm, margin crenate; stamen orange to yellow, 15–40(–60) by 5–7 mm, anther 4–7(–12) mm long. Capsule subterranean, ellipsoid, 6–12 by 4–7 mm. Seeds c. 2 by 2 mm.

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Distribution — North Africa (Egypt); North East Africa (Ethiopia, South Sudan, Sudan); West Africa (Benin, Burkina Faso, Ghana, Guinea, Guinea-Bissau, Ivory Coast, Mali, Niger, Ni- geria, Senegal, Sierra Leone, Togo); Central Africa (Burundi, Cameroon, Central African Republic, Chad, Congo Brazzaville, Congo Kinshasa, Gabon); East Africa (Kenya, Tanzania, Ugan- da); Southern Tropical Africa (Angola, Malawi, Mozambique, Zambia, Zimbabwe).

Habitat & Ecology — Often in savanna woodland (with e.g. Brachystegiae, Primary, etc.), on clayey to loamy soil, or on rocky outcrops, often on ant hills, at elevations of 0–2000 m. Flowering and fruiting: April to December, mostly in October and December.

Field observations — Completely leafless flowering specimens have been collected in May– June and October–De- cember. Information on the labels of Michel & Reed 70 and Schlieben 1560 mentions the appearance of C. spectabilis soon after burning.

IUCN Conservation Status — Least Concern.

Notes — Costus spectabilis can be recognized by its four horizontally spreading leaves forming a cruciform rosette flat on the ground, with an inflorescence in the centre producing large yellow flowers. For morphological differences between C. spectabilis and the only other shootless rosulate species C. macranthus see under the latter. Both C. spectabilis and C. macranthus occur in the region between E28–35° and S6–15° in Malawi, Mozambique, Tanzania, Uganda, Zambia and Zimbabwe.All collections of C. spectabilis have been found in an area where C. macranthus has also been collected. However, C. spectabilis has been collected in a much wider area than C. macranthus : between W13° – E33° and N12° – S15° and therefore in more countries, especially in Western Africa (see map 1 of Lock 1984).

Figures

Plate 4 a. Costus macranthus K.Schum. Habit, flower and details of stamen, stigma and style. – b. Costus nimba H.Maas & Maas. Basal inflorescence. – c. Costus spectabilis (Fenzl) K.Schum.Habit with flowers. – d. Costus lucanusianus J.Braun & K.Schum. Inflorescence with 4 flowers.– e. Costus talbottii Ridl. Flower. – f. Costus louisii H.Maas & Maas. Inflorescence (a: Wright 1905: t 7992; b: Jongkind 11301; c: photographed in Rumonge, SW Burundi, no specimen collected; d: Maas et al. 10000; e: Maas et al. 9800; f: Maas et al. 10339). — Photos: a, b, d–f: P.J.M.Maas; c: E. Fischer.

Map 13 Distribution of Costus macranthus K.Schum. (▲) and C. spectabilis (Fenzl) K.Schum. (●).