Cleisostoma melanorachis

 Cleisostoma melanorachis Aver. & Averyanova 2005, Komarovia 5: 7.

Cleisostoma melanorachis Aver. & Averyanova; Photo by Nguyen Hoang Tuan

Synonyms: 

Cleisostoma crochetii auct. non (Guillaumin) Garay, 1972 p.p.: Aver. & Averyanova, 2003, Updated Checklist Orch. Vietnam: 21. 

Studied collections. 

1985, Averyanov et al., LX-VN S5-96.

Description. 

Epiphyte with pendulous - ascending, rigid, unbranching stem 2—4 cm long, 4—6 mm thick. Leaves 5—8, lanceolate to oblong elliptic, coriaceous, 7—14 by 1—2 cm, unequally 2-lobed at the apex. Inflorescences pendent racemes 20—30 cm long, scape slender, rigid, deep purple-brown to violet-black. Floral bracts triangular acute, 1—2 by 0.5—1 mm. Pedicel and ovary 5—8 mm long. Flowers odorless or with light unpleasant smell, widely opening, tepals yellow-pink, lip and spur purple-violet, side-lobes yellowish-pink to orange, column white to pink-purple, anther cap white to brown-purple. Sepals and petals 5.5—6 mm long; sepals obovate, petals narrowly obovate to lanceolate. Lip tripartite, spurred, about 6 mm from tip of mid-lobe to apex of spur. Side-lobes broadly truncate, at the middle with incurved narrow yellow dent, in front with fleshy purple callus. Mid lobe at wide angle to the spur, fleshy, sagittate, acute, with acute back turned lateral lobes. Spur broadly conical, more or less straight, 3.5 by 1.4 mm. Back-wall callus oblique trapezoidal in sagittal section, lamellate, without significant distal horns. Column straight, 2—2.2 by 0.8—1 mm, at the base with two fleshy inflated purple callosities, rostellum projection narrowly triangular, upward turned. Anther cap hemispherical, 0.8 mm across. Stipe filiform, 2 mm long, suddenly broadening at the apex into two broadly triangular halves. Pollinia 4, ovate, sub-equal, in two pairs. 

Flowering time. 

April-June.

Geographic range. 

Endemic of Vietnam.

Notes. 

Rather common orchid widely distributed in lowland limestone regions of northern Vietnam, mainly at elevations 300—700 m. Small flowers attract few attention and plant easily overlooked during botanical studies and collections.

References:

Leonid V. Averyanov, Nguyen Tien Hiep, Phan Ke Loc, The orchids Of Cuc Phuong National Park Illustrated guide, ISBN: 9781626751514