Species Information - Dendrobium sexcostatum

Dendrobium sexcostatum de Vogel in De Vogel, E.F., van Vugt, R. & Hoogenfdijk, E.A.H., Dendrobium section Diplocaulobium subsection Goniobulbon (Orchidaceae) 1: The Species with 4 or 5 Keels on the Epichile, Malesian Orchid Journal Vol. 22 (2018): 113, fig. 35

Type: Leiden cult. 32024 (Schuiteman, Mulder & Vogel) (holo L)

Synonyms:

Roots filiform, flexuose, to 0.08 cm thick; glabrous. Rhizome short, creeping; rhizome scales completely covering the rhizome, the one around the pseudobulb distinctly longer than the pseudobulb, soon dry and papyraceous, partly decaying, remaining long persistent around the pseudobulbs. Pseudobulbs close together, ascending, ovoid-oblong, 1.5–1.8 by 0.4–0.5 cm; tapering to the top; slightly flattened, 6-ribbed, the ribs on the flatter side closer together. Leaves ovate- oblong, 1.6–2.7 by 0.7–1.1 cm, index c. 2.3–2.4; base narrowed; apex with acute lobules. Inflorescences 1 per pseudobulb, developing in succession, 3–3.5 cm long; peduncle 0.8–1.1 cm long, about as long as or shorter than the spathe; spathe 0.8–1.1 cm long. Pedicel and ovary c. 1.5–1.8 cm long; pedicel terete; ovary with 3 prominent, single-crested ribs. Flower c. 2.5 cm across; sepals and petals white, light yellow in apical half; lip white, extreme base light green, crests light yellow; column cream-coloured, anther light green. Median sepal narrowly triangular, c. 1.5 by 0.35 cm; in top half flat and slightly thickened; apex acute; 5-nerved. Lateral sepals obliquely narrowly triangular, widest at the base, c. 1.5 by c. 0.6 cm in top half flat and slightly thickened; apex acute; mentum conical, obtuse, c. 0.5 cm long; 5-nerved. Petals narrowly linear, c. 1.3 by 0.15 cm; in top half flat and slightly thickened; apex acute; 3-nerved. Lip oblong-ligulate, slightly curved near the base, below 1/3 from the base slightly constricted, when flattened c. 1.2 cm long; 5-keeled; hypochile
when flattened in outline c. rectangular, narrower at the base and there broadly attached, c. 0.5 by 0.3 cm; lateral lobes hardly developed, in front their tip receding; keels 2, rather close together, c. parallel, not very thick, in top 1/3 of the hypochile converging, continuing as lower, thin, plate-like, undulating keels (c. 2 curves) to the top of the hypochile; epichile long semi-elliptic, c. 0.75 by 0.32 cm; top triangular, with acute tip; underside with a low keel from top of the epichile to halfway the lip; median keel undulating, from halfway the claw almost up to 1/3 of the top; inner lateral keels thin, plate- like, much undulating (c. 5 curves) to beyond halfway the epichile; outer lateral keels rather inconspicuous, much lower and shorter than the other keels. Column in lateral view obliquely triangular, c. 0.15 by 0.2 cm, c. 2 cm wide; clinandrium 3-lobulate, lateral lobules broadly triangular, median lobule subulate, c. 0.08 cm long; column-foot c. halfway distinctly curved, in natural position c. 0.5 cm long. Anther bell-shaped, c. 0.12 by 0.1 cm; apex truncate
(After De Vogel in De Vogel, Vugt & Hoogendijk 2018)

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