Thunbergia eberhardtii Benoist (1921: 543)

Do, Van Hai, Nguyen, Thu Thuy, Bui, Hong Quang, Duong, Thi Hoan, Choudhary, Ritesh Kumar & Deng, Yunfei, 2025, Notes on the genus Thunbergia (Acanthaceae) in Vietnam, Phytotaxa 697 (3), pp. 255-264 : 260-262

Thunbergia eberhardtii Benoist (1921: 543) ( Fig. 3 )

Type: — VIETNAM. Hoa Binh, Mai Ha , 8 December 1917, P.A. Eberhardt 4327 (lectotype, designated here: P [P0065033!]; isolectotypes: P [P00650331!, P00650332!]) .

Image of lectotype available at http://coldb.mnhn.fr/catalognumber/mnhn/p/p00650333.

Description: —Vines up to 12 m or more, woody. Stems 4-angled, sulcate, pubescent, soon glabrescent, pilose at nodes. Leaf blade broadly ovate to ovate-lanceolate, 8‒12 × 5‒7 cm, both surfaces glabrous, palmately 5‒7-veined, base cordate, margin remotely dentate or sometimes entire, apex acuminate to acute; petiole 3‒5 cm, puberulent, swollen at base, the ends of the petioles purple for about 0.5 cm, diminishing in length upwards, eventually sessile. Inflorescence of axillary and terminal racemes, erect, 5–8 cm long; peduncles 2–6 cm, pubescent; bracts opposite, lanceolate, green, 12‒15 × 6–8 mm, pubescent on both surfaces, 3‒5-veined, base cuneate, margin dentate or, rarely, entire, apex acute; bracteoles 2, ovate-lanceolate, green, 15‒18 × 8‒9 mm, abaxially tomentose, adaxially pubescent, base rounded to truncate, margin entire, longitudinally 7‒9-veined, apex acuminate; pedicels 9‒10 mm, accrescent to 11 mm in fruit; calyx annular, irregularly many-toothed, 4‒4.5 mm high, tomentose, persistent in fruit; corolla to 2.8 cm, tube yellowish-brown, slightly enlarged tube and obliquely truncate above, outside pubescent with glandular hairs, 5-lobed, lobes ovate-elliptic, 6‒7 × 4‒5 mm, subequal, lower lobes red, upper lobes yellow sometimes with red marginal streaks; stamens 4, didynamous, included, inserted at the middle of corolla tube, filaments glabrous, flattened, anthers 2-thecous; thecae oblong, parallel, difference in height, glabrous except trichome hairs along the line of dehiscence and base of thecae, filaments of shorter pair 6‒7 mm long, anthers 4‒4.5 mm long, upper thecae spurred at base, spurs 2‒2.5 mm long, lower thecae muticous at base, longer pair 7‒8 mm long, anthers 4‒4.5 mm long, both spurred at base, spurs 2‒2.5 mm long; disk thick, annular, yellow, 2.5‒3 mm long; ovary ovoid, ca. 4 × 3.5 mm, densely pubescent, white, 2-locular with two ovules per locule, style 2.8–3 cm long, pubescent, stigma whitish-green, 2-lobed. Capsule with basal part 10‒12 × 14‒16 mm, beak 1.7–2 cm long, pubescent, 4-seeded. Seeds hemispherical, verrucose and glabrous outside.

Phenology: —Flowering and fruiting from August to December.

Habitat and ecology: — Thunbergia eberhardtii is currently known only from a few locations in northern Vietnam. It was observed climbing on shrubs and small trees in the evergreen broad-leaved forests on limestone mountains, at altitudes ranging from 200–600 m a.s.l.

Distribution: — China (Hainan), Laos and Vietnam (Bac Kan Province: Ba Be and Na Ri District, Hai Phong City: Cat Hai District; Hoa Binh Province: Yen Thuy District; Lai Chau Province: Muong Te District; Ninh Binh: Nho Quan District).

Additional specimens examined:— VIETNAM. Bac Kan Province: Ba Be District, Ba Be National Park , elev. 210 m, 22°24’26.3’’N, 105°37’40’’E, 11 September 2020, Do Van Hai et al., MOST 91 (HN) ; Na Ri District, Con Minh commune, Kim Hy Nature Reserve , elev. 597 m, 22°10’18.6”N, 105°02’34.97’’E, 29 September 2022, Do Van Hai et al., VAST09-399 A (HN) ; Hai Phong City: Cat Hai District, Cat Ba National Park , Eo Bua cave , 29 November 1986, Nguyen Huu Hien 779 (HN) ; Hoa Binh Province: Yen Thuy District, Lac Yen Village, Cuc Phuong National Park , 20°23.85’N, 105°33.67’E, 21 August 2000, Nguyen Manh Cuong, Dao Trung Kien, Mai Van Xinh NMC 1019 (HN) ; Mai Ha , 8 December 1917, P.A. Eberhardt 4327 (P) ; Lai Chau Province: Muong Te District, Mu Ca commune, 15 August 2024, Do Van Hai et al., ĐLTB 591 (HN) ; Ninh Binh Province: Nho Quan District, Cuc Phuong National Park , 20 ⁰21.00’ N 105 ⁰35.00’ E, 17 November 1999, D.D.Soejarto, N.M.Cuong DDS 10983 (HN) ; ibid., 105 ⁰36.27’ N 20 ⁰21.17’ E, 22 August 1999, Nguyen Manh Cuong, H.L. Quyen, NMC 431 (HN) ; ibid., 3 August 1971, Dung sine num. (HN) . CHINA. Hainan: Baoting xian, Niujiaoling , 2200 chi, in forest Aug. 9, 1935, F. C. How 73406 ( IBK, IBSC, KUN, MO, PE, SN) ; [Lehui] Lokwui, Scandent in forest, Dec. 9, 1936, S. K. Lau 28346 ( IBK, IBSC, KUN) ; [Lehui] Lokwui , in forested ravine, May 9, 1935, F. C. How 72280 (A, IBK, IBSC) .

Conservation status:— In Vientam, Thunbergia eberhardtii is distributed in the northern part, where the range spans over 30,000 km ². It is primarily found in protected areas, ensuring its conservation. Previously known only from Vietnam, it is now also reported in China and Laos. Based on the IUCN Red List categories and criteria ( IUCN 2024), we propose a status of Least Concern (LC) for this species.

Typification: — Thunbergia eberhardtii was described by Benoist (1921) based on the collection made by P.A. Eberhardt (Coll. no. 4327) from Hoa Binh Province in northern Vietnam. While searching for the original material of T. eberhardtii , three duplicates (P00650331, P00650332 and P00650333) were located. All of them match the original description and are annotated by Benoist, which are syntypes under Ar. 9.6 of ICN. We selected P0065033 as the lectotype as it best represents the diagnostic characters of the species, and other two duplicates (P00650331 and P00650332) become isolectotypes.

Figures

FIGURE 3. Thunbergia eberhardtii. A. Flowering branch, B. Stem, C. Abaxial view of leaves showing morphological variation, D. Part of inflorescence, E-F. Abaxial view of bract, G. Abaxial view of bracts, H. Abaxial view of bracteoles, I. Adaxial view of bracteoles, J. Flower: lateral view, K. Flower: front view, L. Calyx, disk and ovary, M. Calyx (dissected), N. Corolla dissected (outside), O. Corolla dissected (inside), P. Corolla lobes, Q-R. Stamens, S. Disk, ovary and style, T. Stigma: lateral view, U. Stigma: top view, V. Ovary, longitudinal section, showing calyx, disk, W. Fruit, X. Fruit, longitudinal section, Y. Seed, ventral view, Z. Seed, dorsal view (Photos by Do Van Hai and Vu Anh Thuong).