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

Fig. 10 A – F

Type.

DR. Congo, Haut-Katanga, Kasiki , 20–27 Jun 1931, G. H. de Witte 493 (holotype BR [ BR 0000016835344 ]) .

Diagnosis.

Closely related to the species formerly comprising the distinct genus Solenostemon (middle lobes of lower calyx lip fused over most of their length), differing in the beige tomentose flowers, the stem with antrorse hairs, the shortly petiolate leaves with blade truncate at base, upper surface glabrous and with impressed veins.

Description.

Perennial herb or shrub, woody in lower half, height unknown (> 0.40 m). Stem erect, branched, markedly quadrangular, very shortly puberulent with appressed antrorse eglandular hairs and sparse long patent hairs in lower part and also with sparse red sessile glands. Leaves opposite, spreading, petiolate, with or without fascicles of small leaves in the axils; petiole 0.7–1.6 cm long, pubescent like the stem or villous; blade discolorous, broadly ovate-triangular, 2.0–5.0 × 1.4–4.0 cm, base truncate to slightly cordate, apex acute, margin serrate, recurved, teeth rounded, lower surface with very short appressed hairs on veins and softly pubescent to sparsely villous between the veins and with red sessile glands, upper surface subglabrous, veins impressed on upper surface and prominent on lower surface. Inflorescence 5–20 cm long, lax, verticils spaced 10–25 mm, cymes sessile, cincinni 1–2 mm long (pedicel not included), 6–8 flowered, bracts puberulous on outer surface, ovate, cucullate, contracted into a point, ca. 4 mm long, forming a small apical coma, pedicel ascending, 3–4 mm long in fruit, curving at tip, inserted very eccentrically on calyx in front of upper lobe. Flower: calyx ca. 1.5 mm long at anthesis, densely beige tomentose and with red sessile glands, 4–5 mm long in fruit, pubescent all over, tube ca. 1.5 mm long, contracted at throat, sulcate, upper lip purplish, obovate, ca. 2 mm long, curving upwards, obtuse-rounded, margin often irregularly undulate and with 1 tooth on either side and with a short apical mucro, lateral lobes oblong, ca. 1.5 mm long, truncate to rounded, lower middle lobes fused into a lip ca. 2.5 mm long, with two ovate apical lobes contracted into a point; corolla wholly beige tomentose when in bud, ca. 9–13 mm long at anthesis, pubescent to tomentose and with sparse red sessile glands, tube slightly sigmoid, ca. 3.5 mm long, lower lip 4–8 mm long, 2–3 mm deep, cucullate, upper lip 1.5–3 mm long, 4 - lobed; stamen filaments fused, anther ca. 0.7 mm long, style bifid. Nutlets not observed.

Etymology.

The Marungu Plateau, where the type specimen was collected, is a hotspot of biodiversity in DR. Congo.

Distribution.

Endemic to DR. Congo (Haut-Katanga, Marungu Plateau).

Habitat and ecology.

Wetlands, 1850–2200 m elev.

Additional specimens.

DR. Congo, Haut-Katanga, Plateau des Marungu, Env. de Luonde, mare Buzanza, 1850 m elev., 20 Feb 1970, S. Lisowski, F. Malaisse & J. - J. Symoens 10339 ( POZG).

Note.

There is a second specimen in BR labelled “ G. F. de Witte 493 ” [ BR 0000016835351 ]; however, it is a different species, i. e. Equilabium stolzii , that was probably growing intermingled with Coleus marunguensis . Equilabium stolzii is known to occur in wetlands on the Marungu Plateau; the second sheet has been labelled by us G. F. de Witte 493 bis.

Figures

Figure 10. Coleus marunguensis Meerts & A. J. Paton A habit B detail of pubescence of leaf undersurface C detail of inflorescence D fruiting calyx E flower F flower bud (A, B, C, E G. H. de Witte 493 D, F S. Lisowski, F. Malaisse & J. - J. Symoens 10339 a). Drawn by Hilde Orye. Scale bars: 1 cm (A); 1 mm (B, C, D, F); 5 mm (E).