Coleus mitwabaensis Meerts & A. J. Paton, 2024

Meerts, Pierre J. & Paton, Alan J., 2024, The genus Coleus (Lamiaceae) in Central Africa (Democratic Republic of the Congo, Rwanda, Burundi), with the description of 15 new species, PhytoKeys 246, pp. 71-178 : 71-178

Coleus mitwabaensis Meerts & A. J. Paton sp. nov.

Fig. 12 A – F

Diagnosis.

Differing from all other species by the following combination of traits: corolla yellow, rootstock a small tuber, leaves not exceeding 2.7 × 1.0 cm.

Type.

DR. Congo, Haut-Katanga, Kaziba ( rive gauche Mweleshi, affluent rive gauche Senze ), 1140 m elev., forêt katangaise, 12 Feb 1948, G. F. de Witte 3333 (holotype BR [ BR 0000017707961 ]; isotype K) .

Description.

Perennial herb, with a single shoot, 0.12–0.40 (– 0.50) m high, from a globose to irregularly knobby ovoid tuber ca. 10 mm diam. Stem erect or more or less straggling, puberulent, with very short patent or retrorse eglandular hairs and yellow sessile glands; inflorescence axis abruptly becoming densely covered with purplish papillae and very short glandular hairs. Leaves opposite, spreading to ascending, occasionally grouped near stem base, blade mostly elliptic to narrowly elliptic, the lowermost ones shorter, obovate to obovate-elliptic, (1.0 –) 1.5–2.7 × (0.1 –) 0.3–1.0 cm, base cuneate to attenuate, apex obtuse to rounded, subglabrous above or strigillose (with short upward pointing hairs), very shortly appressed pubescent on veins beneath, with pale sessile glands, margin shallowly crenate to entire, very narrowly recurved, papillate to ciliolate, ca. 3 pairs of secondary veins diverging at a very acute angle; petiole 0 (– 0.3) cm. Inflorescence terminal, lax, unbranched or with 1 or 2 branches at lowermost node, 5–15 cm long, rachis with short papilliform hairs, glandular and eglandular, often reddish tinged, verticils spaced 5–15 mm, 2 - flowered, flowers solitary in the axil of each bract, bract narrowly ovate, ca. 1 mm long, more or less persistent, pedicel 1–2 mm long, inserted slightly eccentrically. Flower: calyx at right angle with the pedicel, tubular, with pale sessile glands, short glandular hairs and conical papilliform purplish hairs on veins, ca. 3 mm long at anthesis, accrescent to 4–5 mm in fruit, throat truncate, posterior lobe ovate-triangular, ca. 1–1.5 mm long, not decurrent, lateral lobes triangular ca. 2 mm long, median lobes of lower lip narrowly triangular, ca. 2.5 mm long, with the sinus between median lobes deeper than between median and lateral lobes. Corolla yellow, 10–13 mm long, tube slightly curved to almost straight, widening from base to throat, ca. 3 mm diam. near throat, upper lip ca. 1 mm long, lower lip shortly pubescent, with yellow sessile glands and thin flexuous marginal cilia, ca. 4 mm long, cucullate, ca. 2 mm deep, enclosing stamens. Nutlets globose, very slightly compressed, brown, ca. 1 mm diam.

Etymology.

Mitwaba Plateau, in the north of Upper Katanga, where the type specimen was collected, hosts a very original flora.

Distribution.

Endemic of SE DR. Congo (Haut-Katanga, Mitwaba Plateau).

Habitat and ecology.

Savannah, seasonally moist soil on river banks, miombo woodland; 1140–1400 m elev.

Additional specimens.

DR. Congo, Haut-Katanga, Route Mitwaba-Manono, km. 45, riv. Kalumengongo (zone Mitwaba), 1140 m elev., 8 ° 19 ' S, 27 ° 16 ' E, sable périodiquement inondé en bordure de rivière, 3 Feb 1986, P. Bamps & F. Malaisse 8613 ( BR); Kankunda (affl. rive gauche du Lupiala), 1400 m elev., forêt, 26 Nov 1947, G. F. de Witte 3104 ( BR); Route automobile pour le Shinkulu, 1450 m elev., savane arbustive, 21 May 1948, G. F. de Witte 3863 ( BR, K).

Notes.

1. C. mitwabensis is strikingly distinct on account of the yellow corolla, tuberous rootstock, small leaves and 2 - flowered verticils.

2. Vernacular name: tulamalama, sansala (in kiluba).

3. The sap is used to impregnate fishing nets to attract fish. The tubers are edible.

Figures

Figure 12. Coleus mitwabaensis Meerts & A. J. Paton A habit B detail of stem pubescence C leaf undersurface D detail of rachis pubescence E fruiting calyx F flower G detail of corolla pubescence. P. Bamps & F. Malaisse 8613. Drawn by Hilde Orye. Scale bars: 1 cm (A); 1 mm (B, D, E, G); 2.5 mm (C, F).