Clerodendrum silvanum f. silvanum

Meerts, Pierre, 2023, The genus Clerodendrum (Lamiaceae) in the flora of Central Africa (D. R. Congo, Rwanda, Burundi), Phytotaxa 594 (1), pp. 1-42 : 28-29

21a. Clerodendrum silvanum f. silvanum

Sarmentose shrub or liana up to 20 m. Stem glabrous to papillate, pale greyish-brown, lenticellate, up to 3 cm diam., solid, with persistent petiole bases up to 15 mm long. Leaf: petiole 0.7–3.0(–5.5) cm, canaliculate, glabrous, wrinkled; lamina elliptic, obovate-elliptic, more rarely ovate, 6–20 × 2–12 cm, base cuneate, apex acuminate, wholly glabrous, 5–7 veins on either side, upper surface dark green, generally glossy, reticulum prominulent, lower surface paler, margin entire. Inflorescence terminal on leafy twigs and/or lateral on old wood, often near the ground; peduncle 3–25 cm, glabrous to papillate; a thyrse 3–13 × 3–4.5 cm, mostly lax and longer than wide, occasionally more or less condensed to hemispheric or subcapitate; rachis brownish-grey, lenticellate, smooth or papillate or puberulous, 4–10 nodes, lateral branches at right angles, 5–12(–26) mm, sometimes thickened and flattened due to coalescent pedicels, cymules 3– 10-flowered. Flowers: pedicel 2–5 mm, glabrous, papillate, or, more rarely, puberulent; calyx tubular to narrowly campanulate, 5–9 mm long, 2–4 mm wide at throat in herbarium, thinly striate, lobes triangular 1.5–2 mm long; corolla white to cream, tube 7–18 mm, glabrous, lobes 3–5 mm long, with sessile glands on outer surface; stamens exserted 5–15 mm, anther ca. 1 mm long, brown-violet. Fruit 10–12 × 7–8 mm, dark green turning black, subtended by cupuliform, whitish, fleshy calyx ca. 9 × 8 mm.

Distribution in Central Africa:—D.R. Congo, Rwanda, Burundi.

Distribution elsewhere:— Angola, Cabinda, Cameroon, Central African Republic, Congo, Gabon, Ghana, Guinea, Gulf of Guinea Is., Ivory Coast, Kenya, Liberia, Nigeria, Sierra Leone, Tanzania, Uganda, Zambia.

Habitat:—Rainforest, riparian forest, various types of secondary forest, forest fringe; 100—2500 m.

Selection of representative specimens:—D.R. CONGO. Mayombe: Luali, 26 August 1913, Bequaert 635 (BR!); Luki, 15 October 1948, Donis 2047 (BR!); Ganda-Sundi, August 1919, Goossens 1204 (BR!). Kasaï: Zongo, 19 July 1953, Callens 4171 (BR!); Kiyaka, Kwango, 14 March 1956, Devred 2894 (BR!). Bas-Katanga: Région de Mobanga, Sumaili, 17 June 1952, Germain 7869 (BR!). Forestier Central: Kisangani, 13 September 1971, Bokdam 3194 ( WAG); Yabahondo, October 1952, Germain 8113 (BR!); Kipapashi-Madiwe, October 1938, Gille 138 (BR!); Kisangani, 28 August 1980, Nyakabwa Mutabana 3122 (BR!). Lac Albert: Djugu, September 1931, Lebrun 3914 (BR!). Lacs Edouard et Kivu: Territ. Kalehe. Km 40 route Kavumu-Walikale, 23 June 1955, Christiaensen 924 (BR!); N’Lulu (?), 11 February 1934, de Witte 1397 (BR!); Presqu’île Kasirusiru, 11 April 1951, Pierlot 128 (BR!). Haut-Katanga: Parc National de l’ Upemba. Lusinga, 19 March 1948, de Witte 3554 (BR!); Route Katanga-Mangombo, 9 September 1986, Malaisse 13826 (BR!); Keyberg, 13 February 1963, Schmitz 8169 (BR!).— RWANDA. Rwanda-Burundi: Mbuye, 28 June 1978, Raynal 20765 (BR!).— BURUNDI. Rwanda-Burundi: Kiofi Mosso, 15 March 1952, Michel & Reed 1378 (BR!); Kininya Mosso, 18 June 1952, Michel 2925 (BR!); Marais de l’Akagoma , Ngozi, 11 June 1986, Bouharmont 18128 (BR!).

Notes:—1. Distinction of C. silvanum and C. tanganyikense . C. silvanum is very closely related to C. tanganyikense , as already pointed out by Verdcourt (1992), and intermediate specimens are occasionally found. Inflorescence position (cauliflorous at shoot base, or terminal on leafy twigs) and habit (liana or shrub) are variable within either species. After examining copious materials, we consider the following combination of traits as the most efficient to discriminate the two species:

Based on this combination of traits, Clerodendrum thonneri G ü rke, previously synonymized with Clerodendrum silvanum , is better placed in Clerodendrum tanganyikense (petiole pilose). Clerodendrum silvestre B.Thomas can be interpreted as an intermediate between the two species.

2. Intraspecific variation of Clerodendrum silvanum . C. silvanum is quite variable for length of calyx and corolla, and architecture of the thyrse (lax or congested). Verdcourt (1992) recognized two varieties based on corolla tube length ( var. nuxioides and var. buchholzii ) but did not define them in comparison with the type. Fernandes (1998) proposed another infraspecific treatment, based on the relative length of corolla and calyx ( var. silvanum and var. brevitubum ). Actually, variation in the length of the calyx and the corolla is continuous and none of the aforementioned taxa can be satisfactorily circumscribed. Inflorescence density is variable; morphs with congested inflorescence were initially described at species rank; I agree with Fernandes (1998) that such variation does not deserve more than the rank of form ( f. caulanthum ).

3. Much material hitherto referred to as “ Clerodendrum buchholzii ” in Burundi and Rwanda (e.g. in Malaise (1985)) actually belongs in Clerodendrum tanganyikense .

4. Specimens from Rwanda and Burundi tend to have lamina smaller and more ovate than in other regions.

Second-step lectotypification of Clerodendrum silvanum Henriq. Henriques (1892) cited two syntypes: SAO THOME. Bacia de Contador, alt. 1500 m, Quintas; SAO THOME. Nos Angolares na Bacia do Io Grande, alt. 100 m, Quintas. These appear to correspond to three collection numbers: Bacia do Io Grande , 100 m, January 1886, Quintas 995 ( COI00104957 , COI00104958 ; O-V2250468); Bacia do Io Grande , January 1886, Quintas 1011 ( COI00104956 , BR 0000008718396!); Bacia de Contador , July 1888, Quintas 1347 ( COI00104955 ). Thomas (1936) selected Quintas 995 as the lectotype; two sheets have been found in COI, which correspond to that specimen. I select here the most complete specimen as the second-step lectotype ( COI00104957 ).

Lectotypification of Clerodendrum botryoides (Hiern) Baker. Thomas (1936: 70) designated Welwitsch 5662 (K) as the lectotype. This is surprising, because that specimen comprises no inflorescence and therefore does not display the key feature of the taxon; the isotypes in BM and LISU, however, are flowering specimens displaying the congested inflorescence described in the protologue. Remaining syntypes of Clerodendrum botryoides :— ANGOLA. Golungo Alto , Quib ̂lo, May 1856, Welwitsch 5711 ( BM000931421 ; LISU223648 ); Sobato de Mussengue, August 1855, Welwitsch 5714 ( BM000931415 , BM000931414 ; LISU223634 ; LISU223649 ); Golungo Alto, Sobatos Bumba and Bango, September 1855, Welwitsch 5738 ( BM000931413 ; LISU223650 ) .

Lectotypification of Clerodendrum goossensii De Wild. The protologue ( De Wildeman 1920b: 168) cited two syntypes (Goossens 1151 & 1204). Each of them is represented by two sheets in BR. I select Goossens 1204 as the lectotype, more specifically the sheet with well-developed inflorescences at shoot base and at shoot tip, with the long corolla and long stamens mentioned in the protologue. Remaining syntype:—D.R. CONGO. Ganda-Sundi, 25 July 1919, Goossens 1151 (BR0000008970589!, BR0000008970886!; NY, P00442359 (fragm.)).