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

Fig. 14 A – I

Type.

DR. Congo, Bas-Uele, Route Digba-Gwane , 700 m, sur pengbele, Dec. 1945, R. Germain 4397 (holotype BR [ BR 0000016836068 ]; isotype K) .

Diagnosis.

Related to Coleus bojeri and other species formerly referred to the genus Solenostemon on account to the lower calyx lobes fused into a lip, differing in the upper calyx lobe narrowly ovate-triangular, long attenuate, horizontal or somewhat recurved, much exceeding the lower lobes, indumentum papillate and tuberculate nutlets.

Description.

Annual herb ca. 0.3–1.0 m high, not reported to be aromatic; tubers absent or not collected. Stem erect, quadrangular, thinly papillate, simple or branched. Leaves opposite, ascending, often with fascicles of small leaves in the axils; blade narrowly ovate to narrowly elliptic, 3.5–6 × 0.8–1.6 (– 2.2) cm, base attenuate, apex acute, margin crenate, densely papillate on both surfaces and with sessile red glands, 4–6 pairs of veins diverging at a very acute angle, veins prominent on lower surface; petiole 0.5–1.6 (– 2.5) cm long, narrowly canaliculate, occasionally with long patent cilia. Inflorescence terminal, simple, (3 –) 9–16 cm long, lax, verticils spaced 5–25 mm, the uppermost ones contiguous, cymes consisting of two opposite cincinni, ca. 20–50 flowered, subsessile, very short at first, markedly elongating up to 30 mm in fruit and then flexuous, bracts narrowly to broadly ovate, ca. 5–7 × 2–5 mm, cucullate, occasionally with long cilia in lower half, contracted into a 2 mm point, persistent, the uppermost ones forming a coma, the others reflexed; pedicel 0.5 mm long at anthesis, elongating to 1.5 mm in fruit, inserted eccentrically in front of posterior lobe. Flower: calyx campanulate to shortly tubulate, 2 mm at anthesis, accrescent up to 4–5 mm in fruit, very shortly pubescent and with red sessile glands, tube truncate, upper lobe narrowly ovate-triangular, long attenuate, horizontal or somewhat recurved, much exceeding the lower lobes, margin occasionally ciliate, shortly pubescent also on inner surface, lateral lobes of lower lip triangular, ca. 1.2 × 1 mm, obtuse, median lobes fused for most of their length into a triangular lip ca. 1.5 × 1.5 mm, with 1 or 2 apical teeth; corolla blue or pale mauve, ca. 8 mm long, tube ca. 3 mm long, slightly curved, upper lip perpendicular, ca. 2–3 mm long, lower lip ca. 5 mm long, 2 mm deep, shortly pubescent, occasionally with sessile red glands, stamens fused. Nutlets almost globular, ca. 0.9 mm in diam., light brown, verrucose-tuberculate.

Etymology.

Pengbele (also spelled pembele) is the local name of the particular vegetation type in which the species occurs i. e. open herbaceous vegetation on seasonally flooded lateritic crust ( Bamps 1975).

Distribution.

N DR. Congo, Central African Republic.

Habitat and ecology.

Open savannah, scrub, seasonally moist soil on lateritic crust with impaired drainage in the rainy season and drying out in the dry season (pengbele); 600–700 m elev.

Additional specimens.

DR. Congo, Ubangi-Uele, Région de Gwane, sur pengbele, 8 Jul 1955, R. Boutique 148 ( BR); Bas-Uélé, en savane, 13 Oct 1934, A. De Wulf 264 ( BR); Tukpwo, sur pengbele, 1 Aug 1953, P. Gérard 989 ( BR); Tukpwo, savane, 17 Apr 1954, P. Gérard 1269 ( BR); Tukpwo, sur cuirasse latéritique, Nov 1945, R. Germain 4281 ( BR); Tukpwo, un peu au-delà de la bifurcation de Bengo, îlot forestier sur pembele, 18 Jun 1942, Gilbert in H. Dubois 100 ( BR).

Central African Republic, Oubangui-Chari, Haute-Kotto, entre Zazo et Lutari (?), plateau de latérite, 30 Oct 1921, G. Le Testu 3385 ( BR); Région de Zemio-Obo, à Obo, 27 Dec 1963, B. Descoings 11936 ( MPU); Entre Kitessa et Zemio, 01 Jan 1964, B. Descoings 12365 ( MPU); entre Zemio et Rafaï, dalle latéritique suintante à 21 km à l’ouest de Zemio, 01 Jan 1964, B. Descoings 12407 ( MPU); route entre Zemio et Rafaï, à 48 km à l’ouest de la Ouarra, 03 Jan 1964, B. Descoings 12502 ( MPU).

Notes.

Vernacular name: akonki-pia (in azande).

Figures

Figure 14. Coleus pengbelensis Meerts & A. J. Paton A habit B detail of lower surface of leaf blade C detail of infrutescence D detail of pubescence of inflorescence branch E detail of tip of inflorescence with bracts F flowering calyx seen from below G fruiting calyx, side view H corolla I nucule (A A. De Wulf 264 & G. Le Testu 338 (roots) B A. De Wulf 264 C G. Le Testu 338 E A. De Wulf 264 D, F I R. Germain 4397). Drawn by Hilde Orye. Scale bars: 1 cm (A); 1.4 mm (B); 2 mm (C); 0.28 mm (D); 2.5 mm (E); 0.67 mm (F); 0.5 mm (G); 1.9 mm (H); 0.4 mm (I).