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

Fig. 13 A – E

Type.

DR. Congo, Haut-Katanga, Parc national de l’Upemba, Ganza, près de la riv. Mware , 24 Jun 1949, G. F. de Witte 6990 (holotype BR [ BR 0000016835726 ]; isotype K) .

Diagnosis.

Closely related to Coleus efoliatus De Wild. , differing in the long patent smooth hairs on the calyx, pedicel and rachis, the shorter, more congested, inflorescence and the calyx lobes all similar in shape.

Description.

Annual herb, ca. 0.3 m high, leafless at flowering. Stem erect, sharply quadrangular, puberulent (hairs appressed, antrorse), with a tuft of hairs at the nodes, shiny, with yellow sessile glands, sparingly branched. Leaves not observed. Inflorescence lateral, moderately congested, 6–20 mm long, peduncle ca. 5 mm long, 9 to 20 flowers arranged in a spiral, with a single flower between an opposite or subopposite pair, each bract subtending a single flower; rachis with straight, smooth 1–4 mm long long cilia and short glandular hairs; bract narrowly elliptic, ca. 0.3 mm long; pedicel 1–2.5 mm long, pubescent as the rachis, inserted eccentrically in front of upper calyx lobe; calyx tubular, 3–4 mm long at anthesis, slightly accrescent to 4–5 mm long in fruit, pale whitish-green with dark green veins, with patent smooth cilia 2–5 mm long, short glandular hairs and sessile yellow glands, tube truncate, lobes purplish-tinged, all lobes almost similar in shape and length, narrowly triangular-subulate, 1–2 mm long, upper lobe slightly recurved, not decurrent; corolla sky-blue, ca. 6 mm long, tube straight, ca. 3 mm long, not exceeding calyx, progressively widening to throat, upper lip ca. 1 mm long, sparingly pilose, anterior lip ca. 2 mm long, 1 mm deep, cucullate, sparingly pilose, stamens included. Fruit: Nutlets rounded, compressed, shiny brown, ca. 0.8 mm diam.

Etymology.

Latin mystax - acis, whisker, on account of the long stiff hairs on calyx and pedicel.

Distribution.

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

Habitat and ecology.

Steppic savannah, miombo woodland, often on rocky soil; 1100–1400 m elev.

Additional specimens.

DR. Congo, Haut-Katanga, Colline de Kungumarembe, à l’Est de Kasompi, forêt claire à Brachystegia floribunda , 30 Jul 1956, P. Duvigneaud & J. Timperman 2183 E ( BRLU); Entre Shinkolobwe et Tantara, forêt claire sur roches dures, 7 Sep 1956, P. Duvigneaud & J. Timperman 2643 H ( BRLU); Jadotville [Likasi], forêt claire à Brachystegia utilis sur grand conglomérat, 15 Jun 1957, with Coleus efoliatus, P. Duvigneaud 3580 C 1 ( BRLU); 7 km à l’ouest de Nzilo, sur la piste Nzilo-Kyamasumba, 1200 m elev., forêt claire sur affleurement rocheux, 17 Jun 1984, M. Schaijes 2323 ( BR).

Notes.

1. C. mystax is closely related to C. efoliatus , with which it sometimes co-exists; it shares with it the annual habit, early deciduous leaves, strongly quadrangular stem, inflorescence architecture and short corolla. It differs from it in the very conspicuous long smooth cilia on inflorescence (vs. cilia lacking or occasionally sparse in C. efoliatus ), the calyx lobes all more or less equal in size and shape (vs. upper lobe ovate), the shorter, more congested inflorescence (6–20 mm long vs. 15–50 mm) and the shorter calyx (4–5 mm long vs. 5–10 mm).

2. Vernacular name: tulamalama (in the Upemba National Park).

Figures

Figure 13. Coleus mystax Meerts & A. J. Paton A habit B detail of stem C inflorescence D fruiting calyx E corolla. G. F. de Witte 6990. Drawn by Hilde Orye. Scale bars: 1 cm (A); 2 mm (B, C); 0.8 mm (D); 1 mm (E).