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

Fig. 17 A – F

Type.

Burundi. Usumbura [Bujumbura], 800 m elev., Dec 1934. A. Becquet 834 (holotype BR [ BR 0000016830684 ]; isotype K) .

Diagnosis.

Differing from all other Coleus species by the following combination of traits: leaves grouped in the lower third of the shoot, almost forming a rosette, roots produced into fusiform tubers, cymes (3 –) 4 - flowered.

Description.

Perennial herb, somewhat succulent, aromatic (scent reminiscent of Lavandula ), 0.2–0.5 m high; roots dilated into fusiform tubers up to 40 × 8 mm. Stem erect, leafy in the lower third, quadrangular, sulcate, with patent eglandular hairs and shorter glandular hairs, these denser in the inflorescence, simple or sparingly branched in the inflorescence. Leaves present at flowering, at three to four nodes in the lower part of the shoot, with short internodes and often almost rosulate, spreading, with or without fascicles of small leaves in the axils; blade ovate-elliptic to elliptic or obovate-elliptic, (3 –) 6–13 × (1 –) 2–7 cm, base obtusely cuneate to attenuate, apex obtuse to rounded, margin undulate to shallowly crenate, ca. 6 secondary veins on either side diverging at an acute angle, main veins flattened on lower surface, upper surface velvety pubescent, lower surface tomentose to villous and with red sessile glands; petiole canaliculate, 2–4 (– 5) cm long, long pubescent to villous. Inflorescence terminal, lax, (9 –) 12–28 cm from lowermost node, simple or branched at the lowermost node, verticils laxly disposed, spaced 1–2 (– 4) cm, cymes sessile, 3–4 - flowered; bracts broadly ovate, rounded at tip, ca. 2 × 2 mm, soon caducous, not forming a coma; pedicels 1–2 mm long, elongating to 4–5 mm in fruit, ascending to patent, curved near apex, shortly pubescent and with sparse glandular hairs, eccentrically inserted on calyx in front of upper lobe. Flower: calyx campanulate, at anthesis ca. 2 mm long, in fruit 4–5 mm, pubescent with broad-based short hairs on the veins and with sparse orange or red sessile glands, teeth margin ciliolate, inner side papillate, with pedicel attached asymmetrically in front of upper lip, throat truncate to slightly oblique, posterior lip broadly obovate to almost rounded, 2–3 × 2–3 mm, apex rounded to apiculate or emarginate, curving upwards, not or shortly decurrent, lateral lobes midway between upper lip and median lobes of lower lip, triangular, ca. 1.2 mm long, margin narrowly recurved, median lobes narrowly triangular, ca. 3 mm long, curving upwards in fruit; corolla pale mauve to blue, (10 –) 12–15 mm long, sparsely pubescent, obliquely hanging, tube almost straight to slightly sigmoid, subglabrous, 5–6 mm long, progressively dilated near throat, upper lip 2–3 mm long, shortly pubescent, lower lip shortly pubescent, 5–7 mm long, ca. 2 mm deep, enclosing stamens, anthers ca. 0.5 mm long, round; style bifid. Nutlets brown, shiny, rounded, slightly compressed, ca. 1 mm diam.

Etymology.

All collections of the species originate from the Ruzizi River plain.

Distribution.

E DR. Congo (Kivu) and W Burundi; endemic of the Ruzizi River plain.

Habitat and ecology.

Savannah, steppe, often on rocky or sandy soil; association à Loudetia simplex et Crabbaea velutina ; 800–950 m elev.; flowers in the first half of the rain season.

Additional specimens.

DR. Congo, Lacs Edouard et Kivu, Plaine de la Ruzizi, route Costermansville-Uvira, 20 Feb 1950, R. Germain 6159 ( BR); Plaine de la Ruzizi, savane à Heteropogon-Chloris, 24 Feb 1950, R. Germain 6234 ( BR); Plaine de la Ruzizi, Nyakikumba, env. 900 m elev., savane arborée brûlée, Nov. 1948, F. L. Hendrickx 5678 ( BR); Plaine de la Ruzizi, ca. 800 m elev., env. d’Uvira, Jan. 1929, H. Humbert 7314 ( BR, P); Matiaso, 28 Dec 1950, P. Liégeois 347 ( BR).

Burundi, Ferme de la Randa, 03 ° 07 ' S, 29 ° 22 ' E, 950 m elev., prairie en pente faible, pâturée, 14 Nov 1965, J. Lewalle 16 ( BR, MO); Ruzizi, km. 35, prairie sableuse, 25 Nov. 1967, J. Lewalle 2401 ( BR); Plaine de la Ruzizi, Ruziba, 900 m elev., savane arbustive, 5 Dec 1969, J. Lewalle 4152 ( BR); Bubanza, Cibitoke, 900 m elev., steppe rocheuse, 21 Feb 1971, M. Reekmans 149 ( BR); Bubanza, Cibitoke, steppe rocheuse, 21 Nov 1971, M. Reekmans 1183 ( BR); Bujumbura, Randa, savane, 900 m elev., 30 Jan 1972, M. Reekmans 1499 ( BR); Bubanza, Kagongwe, vallée Katunguru, 26 Nov 1972, M. Reekmans 2136 ( BR, K).

Notes.

1. C. ruziziensis has a very original combination of characters, i. e. fusiform tubers, a rosette of ovate leaves and 4 - flowered cymes. Calyx characters are close to C. hadiensis . It superficially resembles Orthosiphon allenii in having a rosette and tubers.

2. Vernacular name: mwendekere (in kirundi); katjudju, mutuzo (in bashi).

Figures

Figure 17. Coleus ruziziensis Meerts & A. J. Paton A habit B roots with tubers C detail of inflorescence D fruiting calyx E flower F detail of pubescence of leaf undersurface A A. Becquet 834, M. Reekmans 149, H. Humbert 7314 B, C, D A. Becquet 834 E J. Lewalle 2401 F J. Lewalle 2401). Drawn by Hilde Orye. Scale bars: 1 cm (A, B); 2 mm (C, E, F); 1 mm (D).