Vadensea testui Jongkind & O.Lachenaud, 2019

Jongkind, Carel C. H. & Lachenaud, Olivier, 2019, Vadensea (Icacinaceae), a new genus to accommodate continental African species of Desmostachys, Phytotaxa 405 (5), pp. 237-247 : 242-245

3. Vadensea testui Jongkind & O.Lachenaud , sp. nov. ( Figs. 4 & 5 )

Diagnosis:— Vadensea testui resembles V. vogelii , but differs by its calyx lobes being much shorter than the tube ( V. vogelii has calyx lobes longer than the tube), and the absence of a disk around the base of the ovary.

Type:— GABON. Ngounié: Ibaba , 22 March 1930 (fl), Le Testu 8045 (holotype, 3 sheets, P04495106!, P04495107!, P04495108!; isotypes BM011025756!, BR0000024565141 !, K!, WAG.1463135!) .

Tree or shrub 3–10 m high. Twigs, and leaves in bud, completely covered with short, appressed hairs. Petiole 4–15 mm long, with short, appressed hairs. Leaf blade elliptic, 100–230 × 40–100 mm, acute at base, acuminate at apex, coriaceous, glabrous adaxially or with a few hairs on the midrib, abaxially with scattered, short, appressed hairs, usually drying olive green adaxially and yellowish green abaxially; 5–8 pairs of main laterals, strongly ascending; tertiary nervation reticulate, rather prominent abaxially. Inflorescence a pendulous, ebracteate spike, 40–320 mm long, axillary to markedly supra-axillary, the axis with short appressed hairs. Flowers 5-merous, sessile, distichously arranged and crowded in interrupted, line-shaped areas, with dense short, straight hairs around the place of attachment; calyx green, 2.5–3.0 mm high, with short scattered hairs outside, tube campanulate, 1.7–2.3 × 1.5–2.0 mm, lobes broadly triangular, 0.5–1.0 mm long, acute at apex, much shorter than the tube; corolla white, with dense more or less appressed silky hairs outside, and longer, scattered erect hairs inside, tube 4.5–7.0 × 1.0– 1.5 mm, almost cylindrical, lobes 2–3 × 0.3–0.7 mm, triangular to narrowly elliptic. Stamens exserted, filaments 7–11 mm long, glabrous, white, anthers 0.6–1.0 mm long, glabrous, pale yellow. Ovary hairy; style 8–13 mm long, glabrous. Fruit unknown.

Distribution and ecology:— Equatorial Guinea ( Rio Muni), southern Gabon (Chaillu Massif) and western Congo-Brazzaville (Odzala, Chaillu Massif); evergreen forest on well-drained soils, 500–980 m in elevation.

Etymology:— The new species is named after the French botanist Georges Le Testu, who first collected it in 1930 in Gabon.

Notes:— Material of this species has previously been included in V. vogelii (see that species for more details). The two species are indeed very similar, but differ by the characters mentioned in the diagnosis, especially the shape of the calyx ( Fig. 4 ). They also have widely separated ranges, with V. vogelii occurring from Sierra Leone to Ghana, and V. testui about 1500 km to the east, in Equatorial Guinea, Gabon and Congo-Brazzaville ( Fig. 5 ).

Unlike V. vogelii , which is variable in habit, V. testui has never been recorded to climb. The two species are otherwise identical in vegetative characters, and in the absence of fertile material can be separated only on geographical grounds. The other species of the genus, V. oblongifolia and V. tenuifolia , are also quite similar vegetatively to V. testui , but have distinctly thinner leaves with more prominently reticulate tertiary veins; several collections from Gabon and Equatorial Guinea, which lack flowers or fruits, are referred to V. testui based on these characters.

The Sosef et al. 2564 sheet in WAG, cited below, shows something that might be an immature fruit. We do not use it in the description because we are not sure it is not a gall.

Paratypes:— EQUATORIAL GUINEA. Rio Muni : Parc national de Nsork, Obamicu, 26 July 1998 (fl), Lejoly & Esono 98/41 ( BRLU) . GABON. Massif du Chaillu, in between Waka and Lope National Parks, east side of Balendi Hills , Summit, 800 m, 15 March 2007 (fl), Leal, Nguema, Mounoumoulossi & Bissiemou 1565 ( LBV, MO) ; Mt Boutoumbe , centre-est du Parc National de Waka, 10 June 2006 (st), MBG transect 1727 ( BRLU) ; Collines Balendi , est du Parc National de Waka, March 2007 (empty inflor.), MBG transect 1728 ( BRLU) ; Bouvala , ± 14 km E de Mimongo, 6 October 2007 (st), MBG transect 1729 ( BRLU) ; ibid., 13 October 2007 (st), MBG transect 1730 ( BRLU) ; Mouyanama 5 km est vers Youkou, 3 April 1984 (fl), AM Louis 1486 ( BR, LBV, MO, WAG) ; E of Waka National Park, along the road from Mimongo village heading in SE direction, 26 March 2007 (fl), Sosef et al. 2564 ( BR, FHO, K, LBV, MO, WAG). CONGO-BRAZZAVILLE. Odzala National Park, 3 February 1995 (fl), Kouka 63 ( BRLU) ; Zanaga , région Ingolo II, mont N’Doumou, 13 March 1972 (empty infl.), Sita 3328 ( WAG) .

Figures

FIGURE 4. Vadensea testui. A. Flowering branch. B. Flower. C. Flower bud. D. Calyx. E. Flower opened. Vadensea vogelii. F. Flower. G. Flower bud. H. Flower opened. I. Fruit (from spirit). J. Fruit indumentum detail. K. Cross section same fruit. L. Dry fruit. M. Dry fruit indumentum detail. N. Endocarp.A–E: drawn from: Sosef et al. 2564 (WAG); F–H: Jongkind 6232 (WAG); I–K: Versteegh & den Outer 665 (WAG); L–N: de Koning 196 (WAG). Drawn by Hans de Vries, June 2018.

FIGURE 5. Distribution map of Vadensea vogelii (circle) and V. testui (star).