Dendrobium trankimianum T.Yukawa

Averyanov, Leonid V., Ponert, Jan, Nguyen, Phi Tam, Duy, Nong Van, Khang, Nguyen Sinh & Nguyen, Van Canh, 2016, A survey of Dendrobium Sw. sect. Formosae (Benth. & Hook. f.) Hook. f. in Cambodia, Laos and Vietnam, Adansonia 38 (2), pp. 199-217 : 215-216

17. Dendrobium trankimianum T.Yukawa

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 ).

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) .

Figures

FIG. 4. — A-C, Dendrobium chapaense Aver. (25.XI.2015, L.Averyanov s.n.); D, E, D. ochraceum De Wild.; D, CPC 3576; E, HAL 8056; F, G, D. trankimianum T.Yukawa; F, Hon Giao, J.Ponert et al., s.n.; G, L.Averyanov s.n., 2005; H, D. senile E.C.Parish & Rchb.f. (L.Averyanov s.n., IV.2011); I, D. trigonopus Rchb.f. (CPC 1141a). Photos: A-E, G-I, L. Averyanov; F, J. Ponert.