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

Fig. 3 A – F

Type.

DR. Congo. Haut-Katanga, 15 km N de Mitwaba , steppe frais de plaine, 16 Jan 1960, P. Duvigneaud 5082 L (holotype BRLU [ BRLU 0037795 ], isotype K) .

Diagnosis.

Closely related to Coleus foliatus (A. J. Paton) A. J. Paton , differing in the leaves ternate at all nodes, blade longer and narrower, mostly cuneate at base and acute at apex.

Description.

Perennial herb ca. 0.60 m high, with several shoots from a thick woody rootstock. Stem erect, branching only in the inflorescence, rounded near base, rounded to quadrangular in upper part, pubescent to hispidulous, with patent or ascending eglandular hairs and pale sessile glands. Leaves ternate, ascending, subsessile; blade narrowly elliptic, oblong-elliptic to almost linear, 6–9 × 0.5–1.3 cm, length / width ratio ca. 6–10, base mostly cuneate, but almost rounded in upper leaves, apex acute, ca. 8 pairs of secondary veins, margin slightly recurved, distantly serrate, both surfaces somewhat harsh to the touch, pubescent, more densely so on veins underneath, glandular punctate on upper surface, with dense red sessile glands on undersurface; petiole 0–1 mm long. Inflorescence lax to moderately congested at anthesis, laxer at fruiting, paniculiform, with opposite or ternate branches on the uppermost 4–6 nodes of the stem, branches ascending, stiff, 4–12 cm, the longest branches themselves branching; 1 flower in the axil of each bract, lowermost flowers opposite, rachis purplish tomentose, bracts narrowly ovate-elliptic, 3 × 1 mm, obtuse, thin, membranous, pedicels ascending, ca. 2–3 mm long at anthesis, up to 5 mm in fruit, densely pubescent over whole its length, with an inconspicuous joint in the upper third, breaking at the joint at maturity, occasionally not breaking, obliquely adnate to calyx base and eccentrically inserted in front of upper lobe, thickened at fruiting. Flower: calyx ca. 3 mm long at anthesis, densely brownish to purplish pubescent, with eglandular and glandular hairs (these with cup-shaped apical cell in herbarium) and pale sessile glands, campanulate to tubular in fruit, ca. 8–9 mm long, teeth subequal, triangular, acute, the middle lobes of lower lip slightly longer (3 mm long) and more sharply pointed. Corolla blue to purplish, ca. 14 mm long, tube strongly sigmoid, ca. 6 mm long, upper lip 3 mm long, lower lip 8 mm long, 3 mm deep, cucullate, acute at tip, curving upwards, with pale sessile glands and purplish glandular hairs, enclosing stamens and style; anther pouch-like, 1 mm long; style entire. Nutlets ovoid, ca. 1.5 mm long, brown.

Etymology.

Dedicated to Paul Duvigneaud (1913–1991), Belgian botanist, who made important contributions to the knowledge of the flora and the vegetation of Katanga ( DR. Congo).

Distribution.

Endemic of SE DR. Congo (Haut-Katanga); Mitwaba and Kundelungu Plateau.

Habitat and ecology.

Savannah, steppic savannah, often on rocky soil; 1500–1700 m elev.

Additional specimens.

DR. Congo, Haut-Katanga, Sud du point Kisonsa, savane herbeuse, 24 Mar 1954, R. Desenfans 5443 ( BRLU); id., R. Desenfans 5451 ( BRLU); 15 km N de Mitwaba, steppe frais de plaine, 16 Jan 1960, P. Duvigneaud 5082 L ( BRLU); Kundelungu, près du gîte Rack, 5 Feb 1969, S. Lisowski, F. Malaisse, J. - J. Symoens 1058 ( BR) & 1058 a ( POZG); Kundelungu, près du gîte Rack, 5 Feb 1969, S. Lisowski, F. Malaisse, J. - J. Symoens 1247 ( BR) & 1270 ( POZG); same locality, steppe arbustive, 6 Feb 1969, S. Lisowski, F. Malaisse, J. - J. Symoens 1072 ( POZG); Kundelungu, au bord de la rivière Kalembe, steppe à suffrutex, 1550 m elev., 12 Jan 1971, S. Lisowski, F. Malaisse, J. - J. Symoens 12857 ( POZG).

Note.

C. duvigneaudii is very closely related to and arguably only a variety of C. foliatus , differing in the ternate, narrower leaves, blade base cuneate, not clasping, apex acute, blade length / width ratio 6–10 (vs. 3–5 in C. foliatus ). It is also related to the Angolan C. strictipes , differing in the ternate leaves, much more pubescent inflorescence and shorter pedicels. See note under C. foliatus .

Figures

Figure 3. Coleus duvigneaudii Meerts & A. J. Paton A habit B detail of leaf blade undersurface C inflorescence branch D fruiting calyx E flower F detail of corolla pubescence (P. Duvigneaud 5080 L). Drawn by Hilde Orye. Scale bars: 1 cm (A); 1.8 mm (B); 5 mm (C); 1.25 mm (D, E).