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

Fig. 11 A – C

Type.

DR. Congo, Haut-Katanga, 28 km NE de Lubumbashi, Savane de la Luiswishi , 1208 m elev., 30 Aug 1972, J. Bulaimu 520 (holotype BR [ BR 0000017733526 ]) .

Diagnosis.

Related to Coleus modestus on account of inflorescence structure, differing in being a dwarf plant (<10 cm high), leafless at flowering, rootstock a small tuber.

Description.

Perennial herb, 0.04–0.10 m, leafless at flowering, glutinous; rootstock a fusiform tuber 1–2 × ca. 0.5 cm. Stem 1 or several, purplish, erect, simple or branched, terete to subquadrangular, with dense short glandular hairs and sparse eglandular hairs. Leaves not observed. Inflorescence terminal, lax, racemiform, flowers solitary in the axil of each bract, mostly subopposite, bracts linear, ca. 1 mm long, persistent, ciliolate; pedicel 2–3 mm long, extending to 4–5 mm in fruit, slightly ascending to patent, slightly curving downwards at tip, inserted slightly eccentrically on calyx. Flower: calyx 2–2.5 mm long at anthesis, to 4 mm in fruit, with yellow-orange sessile glands and short glandular hairs, tube shortly cylindrical to campanulate, 10 - veined, straight or slightly curved upwards, lobes subequal, narrowly triangular, ca. 1 mm long, the upper one slightly broader, slightly recurved, not decurrent; corolla 5–7 mm long, bluish, with yellow-orange sessile glands, tube straight, ca. 2 mm long, progressively broadening to throat, lower lobe 2.5–4 mm long, ca. 2 mm deep, upper lobe ca. 1.5 mm long, 4 - lobed; anther ca. 0.6 mm; style bifid. Nutlets pale brown, ca. 0.9 mm diam., smooth, flattened, red-speckled.

Etymology.

Latin minusculus - a - um, very small, on account of the dwarf habit of the species.

Distribution.

Endemic of SE DR. Congo (Haut-Katanga).

Habitat and ecology.

Miombo woodlands, savannah; 1200–1300 m elev.

Additional specimens.

DR. Congo, Haut-Katanga, Guba (territ. Lubudi), 30 km E of Kolwezi, dépression incendiée sur terre très dure dans les Mutobo [ Isoberlinia div. sp.], 29 Aug 1956, P. Duvigneaud & J. Timperman 2549 Co ( BRLU); Luiswishi, savane, 20 Sep 1982, F. Malaisse 12350 ( BR).

Note.

C. minusculus is a very distinctive species, on account of its dwarf habit. It shares similarities with C. modestus , which also has tubers, a single flower in the axil of each bract, often subopposite and inflorescence with glandular hairs.

Figures

Figure 11. Coleus minusculus Meerts & A. J. Paton A habit B fruiting calyx C flower. J. Bulaimu 520. Drawn by Hilde Orye. Scale bars: 2 mm (A); 1 mm (B, C).