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

Fig. 9 A – E

Type.

DR. Congo, Katanga, Marungu , 1900 m elev., près du poste Luonde, steppe herbacée, 15 Jun 1969, S. Lisowski, F. Malaisse & J. - J. Symoens 5908 (holotype POZG [ POZG-V-0072834 ]; isotype POZG [ POZG-V-0072833 ]) .

Diagnosis.

Belongs in the group of species formerly comprising the genus Pycnostachys , closely related to Coleus descampsii and Coleus parvifolius , on account of the short, narrow leaves, the very pubescent calyx and the ciliate bracts; it differs in the lack of small leaf fascicles in the axils and in the heteromorphic leaves.

Description.

Perennial herb, 0.50–1.00 m high, rhizome creeping. Stem with a prostrate basal part (0 –) 1–10 cm, rooting at nodes, then abruptly erect, terete to obscurely quadrangular, shortly pubescent with retrorse hairs in lower half, upwardly more or less villous, also with pale sessile glands, simple or sparingly branched only near tip. Leaves opposite or ternate, sessile to very shortly petiolate, heteromorphic, the ones on the lower part of the stem spreading to recurved, ovate-elliptic, obovate-elliptic, to broadly elliptic, 1.5–3.5 × (0.5 –) 1.0– 1.5 cm, the lowermost (juvenile) ones almost round, ca. 0.5 × 0.5 cm, base broadly cuneate to rounded, apex rounded, obtuse or subacute, margin shallowly crenate to subentire, somewhat thickened by a marginal vein, shortly ciliate, with 4 or 5 pairs of secondary veins, arching and more or less parallel to margin, prominulent on both surfaces, shortly pubescent on veins on lower surface, subglabrous on upper surface; petiole 0.1–0.3 cm; leaves on the erect part of the stem ascending to erect, more rarely recurved, subsessile, blade very narrowly lanceolate or oblanceolate-elliptic, to almost linear, 1.8–5.0 × 0.2–0.6 (– 0.8) cm, flat or more or less folded in length, base cuneate to truncate, apex subacute, margin subentire to shallowly crenate distally, ciliate to denticulate, veins 3–5 pairs, prominulent on both surfaces, diverging at a narrow angle and more or less parallel, subglabrous to shortly pubescent on both surfaces (antrorse hairs), more densely so in upper leaves, also with sessile orange and red glands on both surfaces. Inflorescence spicate, capitate to shortly ovoid, 12–30 × 10–16 mm (corolla excluded), apex subacute to obtuse, bracts subtending inflorescence narrowly lanceolate to almost linear, reflexed, persistent, ca. 10 × 0.8–1.5 mm, lower surface villous, upper surface glabrous; bracts of individual flowers purplish, narrowly elliptic to almost linear, the uppermost ones forming a coma, outwardly curving, ca. 4–7 × 0.5–0.8 mm, villous on abaxial surface, densely ciliate, with a fringe of undulate or curly cilia 0.5–1 mm. Flower: calyx tube ca. 2 mm long at anthesis, tomentose and with orange sessile glands, fruiting calyx tube elongating to 4–5 mm long, somewhat compressed on upper side, gibbous on lower side, villous, with long eglandular hairs, also with yellow sessile glands, lobes more or less spreading, ca. 3–4 mm long at fruiting, somewhat flattened and sharp-edged near base, with long curly eglandular hairs ca. 0.6 mm long on margins and outer surface and sessile orange glands, scales at mouth triangular ca. 0.8–1 mm long, somewhat outwardly curving at maturity, with short eglandular hairs; corolla ca. 11–15 mm long, colour unknown (pale coloured in herbarium), tube sigmoid, with a narrow basal part ca. 4 mm long and a broader distal part 3–4 mm long, lower lip 4–6 mm long, pubescent and with yellow-orange sessile glands, upper lip 3–4 mm long, with 4 narrowly triangular lobes. Nutlets pale brown, dull, smooth, ovoid, somewhat compressed, ca. 1.5 mm long.

Etymology.

Dedicated to Stanislaw Lisowski (1924–2002), Polish botanist, who made important contributions to the flora of tropical Africa.

Distribution.

Endemic to the DR. Congo, Haut-Katanga, Marungu Massif.

Habitat and ecology.

Steppic savannah, woodlands, dambos, ca. 1400–2000 m elev.

Additional specimens.

DR. Congo, Haut-Katanga, Marungu, à env. 3 km à l’W de Kasiki, 12 Jun 1969, S. Lisowski, F. Malaisse & J. - J. Symoens 6148 a ( POZG); Plateau de Muhila, bord de la rivière Muizia, 13 May 1971, S. Lisowski 23728 ( POZG); Marungu, 20 km NE de Kapulo, dembo frais dans la forêt claire à Brachystegia , 25 Jun 1957, P. Duvigneaud 3710 P ( BRLU); Entre Kapulo et Pepa, base du plateau des Marungu, muulu autour d’une termitière, 25 Jun 1957, P. Duvigneaud 3713 bis ( BRLU).

Notes.

1. This species is superficially similar to C. lancifolius , on account of the narrow ascending leaves, differing in the capitate inflorescence, the tomentose calyx and the long ciliate bracts. The prostrate basal part of the stem, with broader leaves, is less typical in P. Duvigneaud 3710 P & 3713 bis, but the four cited collections are quite similar in all the other characters and there is little doubt that they are conspecific.

2. There are intermediates with C. descampsii , with very short leaves in some axils, for example, S. Lisowski 23727, 23728 ( POZG), Plateau de Muhila, bord de la rivière Muizia, 1450 m elev., 13 May 1971; S. Lisowski 23719 ( POZG), Plateau de Muhila, 5 km N du poste de Kitu, 1420 m elev., bord marécageux d’un ruisseau, 16 May 1971.

3. S. Bidgood et al. 3358 ( K, P), from Tanzania, is probably the same taxon.

Figures

Figure 9. Coleus lisowskii Meerts & A. J. Paton A habit B inflorescence C bract D corolla E fruiting calyx (A S. Lisowski, F. Malaisse & J. - J. Symoens 6148 a B – E S. Lisowski, F. Malaisse, J. - J. Symoens 5908). Drawn by Hilde Orye. Scale bars: 1 cm (A); 2 mm (B); 1 mm (C, E); 5 mm (D).