Cleisostoma tricornutum Aver.

Cleisostoma tricornutum Aver.; Taiwania 60(3):107‒116, 2015

Cleisostoma tricornutum
Cleisostoma tricornutum

Cleisostoma tricornutum Aver.; Photo Mán Xuân

Vietnamese name: Miệng kín ba sừng

Chinise name:

Common Name: Species name refers to the horn-shaped, forward protruding obtuse lip lobes.

Latin Name: Cleisostoma tricornutum Aver.

Family: Orchidaceae

Synonym Name:


Perennial monopodial epiphytic herb. Stem simple or basally few branched, rigid, curved, suberect or pendulous and ascending, (0.5)1–4(6) cm long, 3-5 mm in diam., with many wiry, flexuose roots at the base; internodes (3)4–8(10) mm long. Leaves rigid, leathery, straight or recurved, sometime somewhat twisted, (3)4–8(10) cm long, (0.6)0.8–1.4(1.6) cm wide, unequally bilobed, with short oblique obtuse lobes. Inflorescence lateral raceme (3)4–12(16) cm long, scape and rachis green to dark purple and almost black; scape 1-8 cm long straight to slightly curved, naked or with 1-3 minute sterile bracts, simple or rarely 1–2 branched; rachis (2)3–7(8) cm long, slightly zig-zag curved, with few to many lax, spirally arranged flowers distant on (2)3–5(6) mm. Floral bracts minute, triangular, acute, about 1 mm long and wide. Pedicel and ovary (2)2.5–5(6) mm long and 0.6–1 mm in diam., yellowish-green to purple, rarely almost white, sometime hardly hairy with sparse small rusty trichomes. Flowers campanulate, not widely opening, 3–3.5(4) mm across; sepals and petals fleshy, dull pale yellowish, sometime with 2 indistinct brown-orange longitudinal bands; lip white or yellowish, with yellow to purple side lobes, median lobe and spur white or yellowish; column white to yellowish, sometime slightly pink at front; anther cap white or yellowish. Sepals broadly obovate, concave, cucullate, obtuse, 2.5–3 mm long, 1.8–2 mm wide. Petals narrowly obovate, obtuse, as long as sepals, 1–1.2 mm wide, forward directed. Lip spurred, 3.5–4 mm long (from spur apex to the apex of median lip lobe), 3-lobed; side lobes narrowly conic, horn-like, obtuse, parallel and forward protruding, 1–1.2 mm long, 0.8–1 mm wide at the base; median lobe triangular sagittate, 1.4–1.6 mm long, 1.8–2.2 mm wide, acute, straight, forward directed; disc with 3 fleshy low indistinct keels; spur broadly conical, saccate, slightly down curved at the base, 1.3–1.5 mm long and wide with entire, round apex and incomplete longitudinal septum inside. Back-wall callus simple, glabrous, in form of laterally compressed boss, indistinctly bilobed adaxially and abaxially. Column short, stout, erect, 1.5–1.8 mm high, 1–1.2 mm wide. Anther cap hemispherical, 0.6–0.8 mm in diam., shortly beaked. Stipe (tegula) 1–1.2 mm long, simple, linear-filiform, slightly widening, curved and conduplicate at apex; viscidium minute, simple in form of flat ovate plate. Pollinia 2, each half-split into 2 subequal hemispheric portions, 0.3–0.4 mm in diam. Fruits narrowly elliptic capsule 1–1.8 cm long, 2.5–3.5 mm in diam., placed horizontally or suberect on rigid stalk 2–3 mm long

Distribution: Vietnam: Ha Giang (Meo Vac), Lai Chau (Sin Ho), Lang Son (Huu Lung), Son La (sine loc.), Thai Nguyen (Vo Nhai), Thanh Hoa (Ba Thuoc; Thuong Xuan). Endemic.

Ecological: Canopy epiphyte. Primary and secondary broad-leaved, mixed and coniferous evergreen shady humid forests on highly eroded rocky limestone, commonly on steep slopes near hill or mountain tops. 100–1600 m. Fl. December – January; July – August. Occasional. Estimated IUCN Red List status – DD.

Type (“8 November 2013 L. Averyanov et al., CPC 6894”) - LE (holotype), Center for Plant Conservation, Hanoi (isotype).

Paratypes: VIETNAM: Ha Giang province, Meo Vac district, Sung Tra municipality, Ta Cha Lang village, L. Averyanov, P.K. Loc, T.V. Thao, P.V. The, N.S. Khang, HAL 8464B (HN, LE); Lai Chau province, Sin Ho district, Xa De Phin municipality, Mao Xa Phin village, P.K. Loc, N.T. Vinh, N.S. Khang, P.N. Quan,d T.A. Suu HAL 8713 (HN, LE, MO); Lang Son province, Huu Lung district, Huu Lien municipality, Huu Lien nature reserve, P.V. The, N.T.Vinh PVT 487B (LE-photo); Son La province, Chu Xuan Canh, s.n. (LE – photo); Thanh Hoa province, Ba Thuoc district, Co Lung municipality, territory of Pu Luong protected area, Co Lung village, N.T. Hiep, L. Averyanov, N.T. Vinh, D.T. Doan HAL 1103 (HN, LE, MO); Thai Nguyen province, Vo Nhai district, Than Sa municipality, Kim Son village, N.T. Hiep, P.K. Loc, L. Averyanov NTH 3889 (HN, LE).

Note: This species may be related to C. crochetii (Guillaumin) Garay (Sarcanthus crochetii Guillaumin, 1956, Bull. Mus. Natl. Hist. Nat. 2 ser. 28: 238), from which it differs in having a simple filiform pollinarium stipe, subglobular pollinia and a hemispheric operculum with a short obtuse beak. Species also has some relation to Cleisostoma parishii (Hook.f.) Garay (=Sarcanthus parishii Hook.f., 1860, Bot. Mag. 86: t. 5217), but differs in having lax inflorescence and long, horn-shaped, lip side lobes. Compared to both mentioned species, the described plant also differs in having distinctly smaller flowers. Cleisostoma tricornutum is common and widespread in many limestone areas of northern Vietnam. It grows at various elevations in forests of any kind. At the same time, this species is easily overlooked in botanical surveys possibly due to the tiny, unattractive flowers, which are the smallest among its congeners. During herbarium processing, flowers and flower buds of this species regularly detach and fall away. This loss on herbarium specimens makes identification and their study problematic. The species exhibits broad variation, particularly in the size of plant and flower, as well as the color scheme of the flowers.






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