Coleus collinus Lebrun & L. Touss.

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 collinus Lebrun & L. Touss. , Bull. Jard. Bot. État Bruxelles 17: 81. 1943.

Figs 1 E, F , 2 A

≡ Solenostemon collinum (Lebrun & L. Touss.) Troupin , Bull. Jard. Bot. Natl. Belg. 55: 299. 1985. Type: DR. Congo, Kivu, Rutshuru, Nov 1937, J. Lebrun 8232 (holotype BR [ BR 0000006262990 ], [ BR 0000006262983 ]; isotype P).

Description.

Annual herb, aromatic, 0.15–0.40 (– 0.60) m, often in groups, rootstock fibrose, without tubers. Stem prostrate or ascending, more rarely erect, slender, occasionally rooting at lower nodes, quadrangular, with long patent multicellular eglandular hairs (ca. 1.5 mm long) and short appressed retrorse hairs, with red sessile glands, simple or much branched. Leaves opposite, spreading to ascending, petiole 0.2–1.1 (– 1.5) cm long, ciliate; blade ovate to trullate, 0.9–2.2 × 0.7–2.0 cm, base obtuse and then shortly attenuate into the petiole, apex acute, margin crenate, 4–6 teeth on either side, with sparse long hairs on both surfaces, dense red sessile glands on the lower surface, ca. 3 pairs of secondary veins. Inflorescence dense at anthesis, then lax at fruiting, simple, 2–5 cm long, ca. 6 mm wide (corollas excluded) at anthesis, elongating to 5–8 cm long, ca. 1 cm wide in fruit, with 4–11 verticils spaced 7–15 mm in fruit, cymes ca. 9 - flowered, peduncle lacking, cincinni 0–4 mm long, ascending, pedicels 2–4 mm long, ascending, with short papilliform hairs, bracts broadly ovate, subsessile, 3–6 × 3–5 mm, foliaceous, the lowermost ones often serrate, persistent, reflexed, margin long ciliate, upper surface glabrous to papillate, lower surface pubescent, with red sessile glands. Flower: calyx shortly pubescent, with red sessile glands, 1–1.5 mm long at anthesis, fruiting calyx ca. 4 mm long, tube shortly campanulate, throat truncate, upper lobe obovate-elliptic, ca. 2 mm long, more or less acute, margin shortly ciliate, recurving, not decurrent, lateral lobes rectangular, truncate to rounded, median lobes of lower lip fused in a linear lip, straight, ca. 3 mm long, with two acute points. Corolla pale blue (rarely white), lower lip deep blue, ca. 2–4.5 mm long, tube 1–1.5 mm long, slightly curved, lower lip ca. 2 mm long, stamens included or occasionally exserted, anthers ca. 0.3 mm long. Fruit: nutlets yellowish to pale brown speckled with red, globose, ca. 0.8 mm diam., smooth.

Distribution.

Cameroon, DR. Congo, Rwanda, Burundi, Uganda, Kenya, Tanzania, Malawi, Zambia.

Habitat and ecology.

Savannah, fallow fields, rocky steppe, pastures, gravel, river banks; 1200–1800 m elev.

Additional specimens.

DR. Congo, Lacs Edouard et Kivu, Luberizi, 1953, A. Gilon 346 ( BR); Rutshuru, Mt. Katale, Dec 1937, J. Lebrun 9154 ( BR, P); Rutshuru, 15 Apr 1937, J. Ghesquière 4291 ( BR); Mumosho, 8 May 1951, J. F. Laurent 223 ( BR).

Rwanda, Kibungo, Gahororo, environs de Zaza, 27 May 1970, G. Bouxin & M. Radoux 2211 ( BR, WAG); Rubona, Inéac, 28 Apr 1958, G. Michel 5332 ( BR, WAG).

Burundi, Bururi, Mosso, Bugiga, 21 May 1980, M. Reekmans 9219 ( BR, WAG); Ruyigi, Kitaba, 15 May 1981, M. Reekmans 10333 ( BR, MO, US, WAG); Gitega, Karuzi, 31 May 1981, M. Reekmans 10517 ( BR, WAG); Kitega Chefferie: Bweru, Environs Karuzi, colline Nyarusange, 16 May 1958, van der Ben 2091 ( BR).

Cameroon, Bamenda, Bambili, Bafut-Ngema, 19 Aug 1951, E. Ujor FHI 29985 ( FHI, K). Uganda, Serere Teso, Dec 1931, Chandler 211 ( K).

Kenya, Trans-Nzoia Distr., Kitale, 19 Sep 1961, Verdcourt 3211 ( EA, K).

Tanzania, Ngara distr., Nyakiziba, 26 Apr 1960, R. E. S. Tanner 4890 ( BR, K).

Malawi. Kondowe to Karonga, Jul. 1896, A. Whyte s. n. ( K).

Zambia, By Katete River, where Great East Road crosses it, 16 Jan 1957, J. M. Wright 124 ( K).

Notes.

1. This species differs from C. bojeri in having persistent bracts, smaller corolla, narrower inflorescence. It often has ascending, somewhat flexuose shoots and smaller leaves, but these traits are more variable.

2. C. collinus is most likely a self-pollinating species, with corollas often not exceeding 1.5 mm long, often cleistogamous and anthers much smaller than in most Coleus species in Central Africa.

3. New species record for Cameroon, Uganda, Kenya, Tanzania, Zambia and Malawi.

Figures

Figure 1. Coleus bojeri complex, details of inflorescence architecture and stem pubescence in four species A, B Coleus bojeri Benth. (T. Sperry 179) C, D Coleus chevalieri Briq. (P. Gérard 4297) E, F Coleus collinus Robyns & Lebrun (J. Lebrun 9041) G, H Coleus heterotrichus Briq. (M. Micha 300). Drawn by Hilde Orye. Scale bars: 1 mm (B, D, F, H); 2 mm (A, C, E, G).

Figure 2. Coleus bojeri complex, leaf shape in four species A Coleus collinus (J. Lewalle 1936) B Coleus bojeri (T. Sperry 179) C Coleus chevalieri (P. Gérard 4297) D Coleus heterotrichus (P. Quarré 3159). Drawn by Hilde Orye. Scale bar: 1 cm.