Coleus welwitschii Briq.

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 welwitschii Briq. , Bot. Jahrb. Syst. 19: 185. 1895.

= Coleus dupuisii Briq. , Bull. Soc. Roy. Bot. Belgique 37: 70. 1899.

≡ Plectranthus dupuisii (Briq.) A. J. Paton , Fl. Trop. E. Afr., Lamiac.: 329. 2009. Type: DR. Congo, Kasai, Mayumbe, Jul 1893, Dupuis s. n. (holotype BR [ BR 0000008109132 ]).

= Solenostemon thyrsiflorum (Lebrun & L. Touss.) Vollesen , Opera Bot. 59: 85. 1980., nom. superfl. Type: Rwanda, Kagera, Nyakayaga, Jan 1938, J. Lebrun 9447 (holotype BR [ BR 0000006263003 ]; isotype K, P).

=? Coleus laurentii De Wild. (1920) 121. Bol. Soc. Ibér. Ci. Nat. 19: 121. 1920. Type: DR. Congo, Gombe, 14 Dec 1903, E. & M. Laurent s. n. (holotype BR [ BR 0000006258580 ] & [ BR 0000008109798 ]).

Type.

Angola, Pungo Andongo, F. Welwitsch 5589 (syntypes BM [ BM 000564040 ], [ BM 000999976 ], C [ C 10001537], G, K, LISU [ LISU 220997], [ LISU 220998], MEL, P), & A. von Mechow 75 (syntype, not seen).

Description.

Paton et al. (2009: 329), Paton et al. (2013: 268), as Plectranthus dupuisii (Briq.) A. J. Paton.

Distribution.

Ethiopia to S. Tropical Africa.

Habitat and ecology.

Savannah, steppic savannah, often on shallow rocky soil, xerophilous scrub, more rarely forest and woodland (termite mounds); 100–2200 m elev.

Additional specimens.

DR. Congo, Côtier, Banana, Mar 1948, H. Callens 1066 (BR); Bas-Congo, Léopoldvile [Kinshasa], Matete, 5 Aug 1956, A. Carlier 334 (BR); Ubangi-Uele, Garamba, 14 May 1950, H. De Saeger 511 (BR); Garamba, route Dungu-Bagbele, km 17 de Bagbele, 27 Aug 1952, G. Troupin 2028 (BR); Lacs Edouard et Kivu, Plaine de la Ruzizi, sommet Tsamate, Apr 1950, R. Germain 6826 (BR).

Rwanda, Bugesera, 27 Mar 1970, G. Bouxin & M. Radoux 1631 ( BR); Rusumo, route vers Nyarubuye, 25 Jan 1980, D. Bridson 299 ( BR, WAG); Kibungo, Rusumo, 16 Oct 1974, J. Lambinon 74 / 1574 ( BR, LG); Route Nyamasheke-Kibuye, 29 Mar 1972, G. Troupin 6510 ( BR, WAG); Kitega, Bweru, Muhweza, 27 Nov 1957, van der Ben 1727 ( BR).

Burundi, Buterama, Gasorwe, 22 May 1959, van der Ben 2558 ( BR); Kameramagambo, 27 Dec 1965, J. Lewalle 155 ( BR, MO); Gitwenge, 2 Jan 1979, M. Reekmans 7448 ( BR); Kagoma, E de Gitwenge, 7 Feb 1979, M. Reekmans 7639 ( BR, WAG); Muramvya, Komwe, 24 May 1981, M. Reekmans 10355 ( BR, MO, WAG).

Notes.

1. Coleus laurentii De Wild. is considered as a synonym of C. welwitschii by Paton et al. (2019). However, the type material ( E. & M. Laurent s. n. [ BR 0000008109798 ], [ BR 0000006258580 ]) is remarkable in being almost glabrous in all vegetative parts; collecting notes on the label indicate the presence of white tubers (not collected); it could represent a different taxon ( C. rotundifolius ?).

2. L. Liben 2855 is somewhat intermediate between C. bojeri and C. welwitschii , having robust lignified shoots, but lacking a true rhizome.

3. Many specimens from Rwanda, Burundi and W Tanzania have greyish-tomentose lower leaf surface and thicker leaves, corresponding to the type specimen of Coleus thyrsiflorus , but there is no real discontinuity with less pubescent forms.

4. See also note under C. brazzavillensis .