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

Fig. 18 A – H

Type.

DR. Congo, Ubangi-Uele, Parc national de la Garamba, Ndelele , colline rocheuse, sol humifère dans les dépressions, 26 Aug 1951, H. De Saeger 1413 (holotype BR [ BR 0000017707787 ]; isotype K) .

Diagnosis.

Related to Coleus bojeri and other species formerly referred to the genus Solenostemon on account of lower calyx lobes fused into a lip, differing by the pedunculate cyme, subglabrous rachis, divaricate zigzagging cincinni, broadly cordiform to reniform foliar blade.

Description.

Annual or perennial herb, 0.5–1.0 m high, more or less tufted, not reported to be aromatic; tubers lacking or not collected. Stem erect or ascending, quadrangular, more or less lignified in lower part, sparingly branched, with a mixed indumentum of very short, papilliform hairs and sparse, long, patent, multicellular hairs, these sometimes almost lacking, also with sparse sessile red glands, becoming subglabrous to papillate in the inflorescence. Leaves opposite, spreading, petiolate, blade broadly ovate to cordiform or almost reniform, shorter than the petiole, (1.0 –) 2.0–4.5 × (0.8 –) 1.8–4.0 cm, apex rounded to subacute, base truncate (in the smallest leaves) to cordate, then shortly attenuate into the petiole, margin often recurved, purplish, strongly crenate to serrate, teeth rounded, ca. 4 / cm, 4–5 secondary veins on either side, densely covered with very short papilliform hairs on both surfaces, also with sparse long hairs, lower surface also with many red sessile glands, reticulum prominent below; petiole 1.5–6 cm long, canaliculate, pubescent like the stem. Inflorescence unbranched or branching at lower nodes, 15–40 cm long, lax, nodes (5 –) 15–60 mm apart, verticils (15 –) 30–50 - flowered, cymes all pedunculate, dichasial, peduncle 5–15 mm, with two divaricate cincinni up to 30 mm long in fruit, zigzagging, with 5–22 flowers, papillate, often purplish; pedicel 0.5–1 mm long in flower, ca. 2 mm in fruit, attached eccentrically behind calyx posterior lip. Flower: calyx ca. 1 mm long at anthesis, pubescent, with red sessile glands, fruiting calyx 2.5–3 (– 4) mm long, shortly tubular or campanulate, papillate and with red sessile glands, throat truncate, posterior lip obovate, ca. 1.5 mm long, obtuse to rounded, apiculate, slightly recurved, not decurrent, lateral lobes rectangular-oblong, truncate to rounded, median lobes of anterior lip linear, fused into a linear lower lip, straight, projecting well beyond the other lobes, with two fine points curving upwards 0.5–1 mm long. Corolla with red sessile glands, (3 –) 8–10 mm long, tube sigmoid, ca. 2 mm long, upper lobe 2 mm long, shortly pubescent, lower lip blue to purple, (2 –) 3–6 mm long, cucullate, 2–3 mm deep, enclosing stamens, shortly pubescent and with red sessile glands, stamens fused in lower half. Nutlets shiny brown, slightly compressed, 0.8–1 mm.

Etymology.

The epithet refers to the characteristic zigzagging rachis of the cymes.

Distribution.

W Uganda and NE DR. Congo.

Habitat and ecology.

Rock crevices, savannah on shallow rocky soil; ca. 700–850 m elev.

Additional specimens.

DR. Congo, Ubangi-Uele, Parc national de la Garamba, Ndelele, fissures et dépressions rocheuses, 27 Sep 1952, H. De Saeger 3849 ( BR); Mont Genze, sur la roche, 30 Sep 1953, P. Gérard 847 ( BR); Entre Faradje et Dungu, savane rocheuse au bord du Kibali, crevasses dans les roches, Aug 1931, J. Lebrun 3458 ( BR, K); Parc National de la Garamba, frontière du Soudan, près de Ndelele, affleurement rocheux, pelouse rase à Cyanotis et Sporobolus , 13 Aug 1952, G. Troupin 1848 ( BR); Forestier Central, Haut-Zaïre, Ituri, env. de Nduye, Mont Mukonza, rochers, 8 Aug 1975, S. Lisowski 40451 ( POZG); Same locality, 5 Jan 1976, S. Lisowski 41509, 41738 ( POZG); Haut-Zaïre, Ituri, env. de Nduye, au-dessus du village Maitatu, Mont Mukonza, 12 Apr 1976, S. Lisowski 42315, 42498 ( POZG).

Uganda, West Nile Distr., Rokosa Hill, ¾ mile SE of Maracha [illegible] Camp, 6 Aug 1953, R. J. Chancellor 113 ( K).

Note.

The specimens from Ituri (region of Nduye), ca. 250 km south of the range of the species in the Garamba Region, match the type in all traits except for the almost straight, not zigzagging cincinni; we consider them as conspecific.

Figures

Figure 18. Coleus zigzag Meerts & A. J. Paton A stem and leaves B inflorescence C detail of petiole apex D detail of pubescence of inflorescence E cyme F fruiting calyx, side view G calyx seen from below H flower (A H. De Saeger 1413 & 3849 B – E H. De Saeger 1413 F, G H. De Saeger 3849). Drawn by Hilde Orye. Scale bars: 1 cm (A, B); 1 mm (C); 1.57 mm (D); 2 mm (E); 0.75 mm (F); 1 mm (G); 1.3 mm (H).