Bulbophyllum tseanum (S. Y. Hu & Barretto) Z. H. Tsi

Li, Lin, Hu, Ai-Qun, Wu, Qiu-Ping, Wu, Kun-Lin, Fang, Lin & Zeng, Song-Jun, 2021, Reconsideration of the taxonomic status of Bulbophyllum obtusangulum (Orchidaceae) from southern China, Phytotaxa 494 (2), pp. 219-224 : 222-223

Bulbophyllum tseanum (S. Y. Hu & Barretto) Z. H. Tsi

Figs 1 , 2

Bulbophyllum tseanum (S. Y. Hu & Barretto) Z. H. Tsi in Fl. Reipubl. Popularis Sin. 19: 239. 1999. ≡ Cirrhopetalum tseanum S. Y. Hu & Barretto in Chung Chi J. 13(2): 30. Fig. 14. 1976. Type: CHINA. Hong Kong, New Territories, Patsin Range, Sha Tau Kok area , S.Y. Hu 13586 (holotype: K!).

= Bulbophyllum obtusangulum Z.H. Tsi in Acta Phytotax. Sin. 33 (6): 578-579, pl. 1, f. 1-4. 1995, Syn. nov.

Type: CHINA. Hainan, Baoting (Poting), in arbore, 900 m, 24 May 1935, F.C. How 72637B (holotype: PE! isotype: IBSC!) .

Emended description. Lithophytic and epiphytic herb. Root fibrous, numerous. Rhizomes creeping, ca. 3 mm in diam., covered by straw-yellow scales. Pseudobulbs obliquely ovoid, unevenly 5-angled, shiny pale green, 1–1.5 cm long, 1.5–2 cm apart, with a terminal leaf. Leaves coriaceous, oblong, 4–9 cm long, 1.4–2.5 cm wide, apex shortly and obtusely bilobed, petiolate, petioles 3–7 mm long, articulate at the base. Inflorescence emerging from base of pseudobulb, 8–15 cm long, bearing 4 or 8 flowers in a subumbellate raceme; peduncle slender, ca. 1 mm in diam., reddish purple, with 2 sterile sheathing bracts; floral bracts subulate, 3 mm long, acuminate. Pedicel and ovary ca. 4 mm, deep red. Flowers with ciliated dorsal sepal and petals entirely reddish brown or dull yellowish marked brownish purple along the margins; lateral sepals yellowish, densely mottled brownish purple or purplish red; labellum glossy orange, often blotched dull brownish purple along margins; dorsal sepal subovate, concave, 5–6 mm long, 4–5 mm wide, margins with dark red fimbriate cilia, apex long caudate, ca. 4 mm long; lateral sepals obliquely linear-oblong, 1.8–3.5 cm long, usually 2.5–3 cm long, 3.5–4 mm wide, twisted near base, with the upper edges connate to each other, tongue-shaped, slightly recurved and obscurely forming an acute angle at the apex; petals oblique ovate, 3–4 mm long, 2–2.5 mm wide, margins fimbriate-ciliate, apex long caudate; labellum ligulate, fleshy, recurved below middle, hinged on the apex of the long column-foot, mobile, 3–3.5 mm long, adaxially with groove along each side and a median longitudinal ridge; column stout, ca. 3.5 mm long, with prominent triangular column wings extending outwards, toothed at the apex; stelidia triangular, ca. 0.3 mm, apex acute; rostellum fleshy, subtruncate; stigma square, deeply concave with a large shiny gland on the upper margin, and a small one on each side of the lower margin; anther cap glabrous and truncate at the apex; pollinia 4 in 2 pairs, the outer one of each pair larger than the inner pair.

Distribution and habitat. So far, the species is known from southern China (Hainan and Hong Kong) and Central Highlands of Vietnam. It occurs in evergreen broad-leaved forests or semi-deciduous forests under the influence of a tropical monsoon climate, growing as an epiphyte on tall old tree trunks along stream valley, occasionally as a lithophyte on mossy rocks, at elevations of 250 to 930 m a.s.l.

Phenology. Flowering during late March and June, especially in May.

Conservation status. In Hong Kong, this species has not been seen in the wild since 1974. Only several locations of Bulbophyllum tseanum are presently known from southeast Hainan, China and central Vietnam. Based on its limited geographical range and fragmented spatial pattern, we tentatively consider it to be Endangered (EN) according to IUCN (2019) categories and criteria.

Additional specimens examined. CHINA, Hainan Province, Baoting County, Mt. Diaoluoshan, Baishui Ridge , 22 Nov. 1954, Diaoluoshan Expedition Team 2589 (IBSC) ; Hainan, Ledong County, Jiaxi Provincial-level Nature Reserve , 14 Jun. 1999, Z.H. Tsi & L. P. Xiao 99618 (PE) . VIETNAM, Thua Thien Hue Province, Phu Loc District, Bach Ma National Park , around point N 16°13’53’’ E 107°49’02’’, 2 May 2003, N.T. Hiep, L. Averyanov, N.T. Vinh et al. HLF 1567 (LE) ; Thua Thien Hue Province, Nam Dong District, Huong Son Municipality , around point N16°10’22’’ E107°36’24’’, 29 March 2005, L. Averyanov, P.K. Loc, P.V. The, A. Averyanova & N.T. Vinh HAL 7065 (LE) ; Thua Thien Hue Province, Nam Dong District, Huong Son Municipality , around point N16°09’58’’ E107°36’07’’, 31 March 2005, L. Averyanov, P.K. Loc, P.V. The, A. Averyanova & N.T. Vinh HAL 7163a (LE) ; Thua Thien Hue Province, A Luoi District, Huong Nguyen Municipality, in vicinities of Tra Ve forest protection station, around point N16°15’27’’ E107°26’15’’, 5 May 2005, L. Averyanov, P.K. Loc, T.V. Thao & N.T. Vinh HAL 7899 (LE) ; Thua Thien Hue Province, Huong Thuy District, Duong Hoa Municipality, Huong Thuy forest enterprise territory, around point N16°12’50’’ E107°36’29’’, 14 May 2005, L. Averyanov, P.K. Loc, T.V. Thao & N.T. Vinh HAL 8259 (LE) .

Figures

FIGURE 1. The type specimens of Bulbophyllum tseanum (A), B. obtusangulum (B–C) and B. lepidum (D–F).A. Holotype of B. tseanum, S.Y. Hu 13586 (K). B. Holotype of B. obtusangulum, F.C. How 72637B (PE). C. isotype of B. obtusangulum, F.C. How 72637B (IBSC). D–F. Types of B. lepidum, Blume 1934 (L).

FIGURE 2. Bulbophyllum tseanum. A. Habitat. B. Inflorescence. C. Close-up of flowers. D. Dorsal sepal, petal and lateral sepal, adaxial view. E. Column, ventral view, showing the anther, the wings and the glands. F. Column, lateral view, showing the wings, the stelidia and the elongated and curved column-foot. G Lip, lateral view. H. Pollinia. Scale bars, 10 mm (D), 2 mm (E, F, G), 0.5 mm (H).