Dendrobium trankimianum T.Yukawa

17. Dendrobium trankimianum T.Yukawa View in CoL

Annals of the Tsukuba Botanical Garden 23: 21, figs 1, 2 (2004). Dendrobium multilineatum auct. non Kerr: R.K. Choudhary et al., Taiwania 57 (2): 225, figs 1, 2 (2012).

TYPUS. — S Vietnam. Borders of Lam Dong, Khanh Hoa and Ninh Hoa Province , 800-1000 m alt., IV.2000, Hort. Tsukuba Botanical Garden accession number 127511 (holo-, TNS).

HABITAT, PHENOLOGY AND CONSERVATION STATUS. — Epiphyte on tall trees in primary closed evergreen broad-leaved and mixed seasonal mountain forest on shale and granite, particularly in cloud forest on mountain tops. (800) 1000-2000 m. Fl. April-May. Very rare. Expected IUCN Red List status – CR.

DISTRIBUTION. — Vietnam ( Khanh Hoa, Lam Dong). Endemic .

MATERIAL EXAMINED. — Vietnam. Khanh Hoa, Giang-Ly, prov. de Khan Hoa, Nha Trang, Poilane 3611 ( P [ P00407645 ]) ; Khanh Hoa, Khanh Son, Hon Giao mt. , VH 4150 ( HN, LE, MO) ; Lam Dong, Dalat area , L . Averyanov s.n. anno 2005 ( LE photo) ; Khanh Hoa, Hon Ba, J . Ponert et al., s.n., III.2012 ( LE photo, PRB photo) ; Lam Dong, Hon Giao, J . Ponert et al., s.n., III.2012 ( LE photo, PRB photo) .

DESCRIPTION

Stems cylindric reed-like to narrowly fusiform, of many nodes, leafy throughout, 30-50(60) cm long, 0.6-1 cm in diameter. Leaves narrowly ovate to oblong, (3)4-8(10) cm long, 0.7-2.2 cm wide. Inflorescences 1-2(3), each with 1-2 flowers; floral bracts elliptic, obtuse, to 10 mm long, 6 mm wide. Pedicel and ovary pale green, about 3 cm long. Flowers odorless, widely opening, 3.5-5 cm across, white; disc bright red; column and anther cap pink. Sepals triangular narrowly ovate, acute to acuminate, 2.8-3.4 cm long 1.2-1.4 cm wide. Petals obovate, acute to round at apex, as long as sepals but usually distinctly broader. Lip shortly clawed, obovate, indistinctly 3-lobed, 3-3.5 cm long, 2-2.5 cm wide; side lobes erect, broadly triangular, obtuse, 1.6-1.7 cm long, 8 mm tall; median lobe oblong, 0.7-1 cm long and wide, finely undulate along margin, shortly apiculate; disc with longitudinal plate splitting distally on medial lobe into 3-5 low straight or finely rugose keels. Mentum narrowly conical, to cylindrical, 1.5- 2.5 cm long. Column 6-8 mm tall, 4.5 mm wide, column foot 7-9 mm long; anther cap cubic, papillose, 3-3.5 mm long and wide ( Fig. 4F, G View FIG ).

REMARKS

According to the author of this species – “ D. trankimianum is closely related to D. draconis but can be distinguished by the following characters: 1) thinner, terete stems; 2) smaller perianth lobes; 3) oblanceolate-obovate petals; 4) more-developed lateral lobes of the labellum; 5) a shorter mid lobe of the labellum; and 6) different callus structure of the labellum”. Actually this species distinctly differs from D. draconis in a much smaller epichile which is narrower than the hypochile and in a flattened lip. According to its floral morphology D. trankimianum looks also to be close to D. kontumense , D. multilineatum , D ochraceum and D. wattii .

In the past this species was observed as an abundant epiphyte on tops of the Hon Giao ridge along the border of Khanh Hoa and Lam Dong provinces ( April 1997, L.Averyanov et al., VH 4150). It was also observed as a common epiphyte on larger trees in mountain forest on peaks of the Hon Ba massif in Khanh Hoa province at elevations above 1350 m (observation of March 2012) .