Coleus celsus A. J. Paton

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 celsus A. J. Paton , Phytokeys 129: 34. 2019 .

≡ Solenostemon robustus Hiern , Cat. Afr. Pl. 1: 864. 1900., non Coleus robustus (Hook. f.) A. J. Paton.

≡ Plectranthus robustus (Hiern) A. J. Paton in Fl. Zambesiaca 8, 8: 234. 2013. Type: Angola, Pungo Andongo, from Lombe to Condo, Mar 1857, F. Welwitsch 5538 (lectotype BM [ BM 00564035] designated here; isolectotypes [ BM 00564268], LISU [ LISU 220992], [ LISU 220993]).

Description.

Woody perennial herb, ca. 1.0– 1.5 m high, more or less leafless at flowering; rootstock with tubers up to 10 × 5 cm. Stem erect, up to 1 cm thick, woody and cylindrical in lower half, striate, lenticellate, puberulous with short eglandular hairs, obtusely quadrangular in upper half, densely white pubescent with short antrorse hairs, branching only in the inflorescence. Leaves opposite, petiolate, ascending, beginning to fall off at time of flowering; blade yellowish-green, coriaceous to somewhat crassulescent, broadly ovate, 4.5–8.5 (– 14.0) × 3.5–6.0 (– 9.0) cm long, base broadly cuneate, obtuse to rounded and then shortly attenuate into the blade, apex rounded to acute or shortly acuminate, margin crenate, not recurved, upper surface subglabrous to puberulous, lower surface shortly pubescent on veins, ca. 6–8 pairs of secondary veins; petiole 0.5–2.0 (– 3.0) cm long. Inflorescence 20–30 cm long, pyramidal-paniculiform, with 5–7 pairs of opposite ascending branches ca. 1.5–7 cm long, spaced ca. 5 cm, each terminating in 1–4 condensed ca. 1.5 cm long racemes, with tomentose to villous rachis; flowers solitary in the axil of each bract, arranged helicoidally around axis, bract ovate, ca. 2 mm long, villous on back, pedicel in fruit (8 –) 18 mm long, jointed ca. 2–5 mm above base and breaking at joint at maturity, leaving persistent base on rachis, pubescent, adnate eccentrically to calyx; calyx campanulate, beige to fulvous villous at first, ca. 5 mm long at anthesis, fruiting calyx (9 –) 13–14 mm long, coriaceous, tube campanulate, pubescent, with pale sessile glands, throat slightly oblique, lobes ciliate, upper lobe ovate-triangular, slightly curved, not decurrent, acute, ca. 2 mm long, lateral lobes of lower lip triangular, ca. 3 mm long, middle lobes of lower lip narrowly triangular ca. 4 mm long. Corolla purplish-pale blue with pale sessile glands, tube strongly sigmoid 7–8 mm long, upper lip ca. 3 mm long separated from lower one by a 3 mm gap, lower lip 9–11 mm long, 4–5 mm deep, cucullate, with two small auricles near base, anther pouch-like, style entire. Nutlets light brown, red speckled, smooth, broadly ovoid, ca. 2 mm.

Distribution.

Angola, DR. Congo.

Habitat and ecology.

Wooded savannah, steppe; 1000–1670 m elev.

Additional specimens.

DR. Congo, Kasaï, Kwango, Village Shamafuka (15 km S de Bwana Mutombo), 1 Apr 1948, P. Duvigneaud 970 E ( BRLU).

Notes.

1. New species record for DR. Congo. The Congolese locality represents the northernmost limit of the species’ distribution range.

2. Lectotypification. Solenostemon robustus Hiern was described most likely based on Welwitsch’s materials at BM. BM holds two sheets of F. Welwitsch 5538. We designate the sheet with complete collecting data on the label as the lectotype.