Coleus homblei De Wild.

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 homblei De Wild. , Contr. Fl. Katanga: 174. & Ann. Soc. Sci. Bruxelles 42 (1): 49. 1921.

= Plectranthus sigmoideus A. J. Paton , Fl. Trop. E. Afr., Lamiac.: 333. 2009., syn. nov.

≡ Coleus sigmoideus (A. J. Paton) A. J. Paton , Phytokeys 129: 97. 2019 . Type: Zambia, track opposite turning to Mbala (Abercorn) Club, H. M. Richards 4353 (holotype K [ K 000070564 ]), syn. nov.

Type.

DR. Congo, Elisabethville [Lubumbashi], brousse, Feb. 1912. H. Homblé 210 (lectotype BR [ BR 0000006262181 ], designated here).

Description.

Short-lived perennial herb 0.20–0.40 (– 0.65) m, rootstock a thin rhizome rooting at nodes, tubers occasionally observed (not collected in Central Africa). Stem erect, quadrangular, with short appressed retrorse hairs (also patent hairs outside Central Africa), yellowish to green, mostly unbranched, rarely with a few erect branches. Leaves opposite, in ca. 5 or 6 pairs, the uppermost pair often much reduced, petiolate, except uppermost pair, ascending, petiole 0.2–2.0 (– 2.5) cm with short retrorse hairs and a few long cilia, blade ovate, ovate-elliptic to subrhombic, 1.2–4.5 (– 5.0) × 0.8–2.5 (– 3.2) cm, apex acute, base cuneate and shortly attenuate into the petiole, margin narrowly recurved, with 4–8 sharp teeth on either side (2–3 mm deep on adaxial side), upper surface pubescent, with a mixed indumentum of antrorse hyaline hairs 0.5–2 mm long and very short papilliform hairs, lower surface very shortly appressed pubescent on veins (hairs often retrorse), also with red sessile glands, 3–5 pairs of secondary veins. Inflorescence lax, 5–13 (– 17) cm long, with 3–9 (– 15) verticils spaced 5–25 mm; bracts narrowly ovate, cucullate, 3–7 mm long, acuminate, forming an apical coma, caducous; cymes ascending to spreading, sessile, with 3–7 flowers on a 0–2 mm long rachis; pedicels ca. 4–6 mm long at anthesis, spreading to slightly ascending. Flower: calyx campanulate, ca. 3 mm long at anthesis, shortly pubescent, with red sessile glands, widely open; fruiting calyx 5–6 mm long, lateral teeth obtuse, ca. 2 mm long, lower teeth fused in a ca. 4 mm long very narrow lip, with two acute tips; corolla pale blue or white, with red sessile glands, ca. 9–13 mm long, tube ca. 5 mm long, strongly sigmoid, lower lip ca. 6–7 mm long, 4 mm deep, upper lip ca. 2 mm long; staminal filaments fused, anther ca. 0.5 mm long. Nutlets brown, red-speckled, ovoid, ca. 1 mm long.

Distribution.

SW Tanzania to Zambia and SE DR. Congo.

Habitat and ecology.

Miombo woodlands, often with Brachystegia microphylla , on shallow rocky soil, termite mounds; ca. 1250–1520 m elev.

Additional specimens.

DR. Congo, Haut-Katanga, Près de Lubumbashi, colline Kiswishi, 24 Feb 1987, F. Billet & B. Jadin 4227 ( BR, UPS); Dilolo, 1935, de Wouters d’Oplinter 3 ( BR); Lubumbashi, route de la mine de l’Etoile, km 12, 19 Apr 1957 P. Duvigneaud 2847 Co ( BRLU); Entre Welgelegen et Kasumbalesa, 29 Jan 1960, P. Duvigneaud 5302 C ( BRLU); Kasombo, 3 Feb 1960, P. Duvigneaud 5384 Col ( BRLU); 12 km NW de Lubumbashi, 12 Mar 1958, A. Gathy 300 ( BRLU); Elisabethville [Lubumbashi], Mar 1912, H. Homblé 220 ( BR) (about this specimen, see note under C. heterotrichus ); Kasapa, 26 Feb 1966, F. Malaisse 4012 ( BR, LSHI); Ferme prince Léopold, 21 Feb 1927, P. Quarré 1032 ( BR); Keyberg, 9 km SW of Lubumbashi, 27 Feb 1948, A. Schmitz 1392 ( BR); 14 km from Lubumbashi, 17 Feb 1966, J. - J. Symoens 12233 ( BR, K, LSHI); Likasi, Panda, 25 Mar 1970, S. Lisowski 23382 ( POZG).

Notes.

1. C. homblei is superficially similar to C. bojeri and was synonymised with it by Paton et al. (2009, 2013). It differs from it in the perennial habit (this often difficult to observe), the more sharply serrate leaf margin, verticils with fewer flowers, longer pedicels and longer calyx at anthesis. The generally unbranched shoot is also typical with only ca. 5 pairs of leaves, the uppermost pair sessile and bracteiform. The species is widespread in miombo woodlands in the region of Lubumbashi.

2. Lectotypification of Coleus homblei De Wild. De Wildeman (1921 b) cited two syntypes, i. e. H. Homblé 210 (syntype BR [ BR 0000006262181 ], [ BR 0000006262518 ]), DR. Congo, Elisabethville [Lubumbashi], brousse, Feb 1912 & H. Homblé 1259 (syntype BR [ BR 0000005201518 ], [ BR 0000005201846 ]), Plateau Biano, Tshisinka, partie boisée, Feb 1913. Both syntypes are unusual in having shoots branched from the base. Both match the protologue. H. Homblé 210 is more representative of the sharply serrate leaf margin and sheet [ BR 0000006262181 ] is designated as the lectotype because the label has “ Coleus homblei ” in De Wildeman’s handwriting.

3. The type materials of Coleus sigmoideus A. J. Paton show the diagnostic traits of Coleus homblei De Wild. , differing only in the presence of tubers, while tubers have not been collected in materials from DR. Congo.

4. See also note under C. heterotrichus .