Orchids of New Guinea

Hymenorchis tanii

Hymenorchis tanii Schuit. & de Vogel, OrchideenJ. 16 (2009) 150, fig.

Type: Leiden cult. 20081490 (de Vogel) (holo LAE; iso L; all spirit material).

Roots glabrous, 0.07–0.18 cm. Stem unbranched, c. 0.5 cm long, rooting at the base. Leaves 4–5, patent, not twisted at the base, elliptic, rigid, very fleshy, with slightly warty upper surface, 1–1.5 by 0.5–0.7 cm; leaf-sheaths short, glabrous, with entire margins; margins smooth or very slightly rough; apex obtuse, minutely bidentate. Inflorescence patent, arising below the lowest leaf, glabrous, almost umbellate, 3–4-flowered, with all flowers opening simultaneously c. 0.7 cm long,; peduncle with two small peduncle-scales in the basal half. Floral bract narrowly triangular, glabrous, 0.25–0.3 cm long; apex acute, conduplicate in apical part. Pedicel with ovary c 0.4 cm long, slender, 6-winged, covered with scattered, hair-like papillae except near the apex. Flowers widely opening, c. 2 cm across, without distinct scent. Median sepal narrowly ovate, 0.85 by 0.31 cm; margin minutely and irregularly dentate 3-veined; strongly keeled outside along the mid-vein; apex acute-acuminate. Lateral sepals obliquely narrowly ovate. 0.1 by 0.33 cm; margin minutely and irregularly dentate; 3-veined, strongly keeled outside along the mid-vein; apex acute-acuminate. Petals obliquely narrowly ovate, 0.91 by 0.27 cm; margins minutely and irregularly dentate; 3-veined, strongly keeled outside along the mid-vein; apex acute-acuminate. Lip spurred, entire, glabrous; blade semi-elliptic, rounded, 0.26 cm long; spur parallel with the ovary, 0.9 cm long, obliquely conical in lateral view, in apical half slightly decurved towards the ovary, obtuse. Column glabrous, 0.33 cm long, helmet-like swollen in the apical part; stigma large, concave, orbicular; rostellum with two subulate arms, 0.1 cm long. Anther cucullate, 0.17 by 0.14 cm; basal part reniform, deeply concave inside; apical part rather flat, 5-angular, subacute. Pollinia 2, subglobose, 0.06 cm diam., with a small pore; stipe narrowly linear-triangular, 0.02 by 0.04 cm, apex obtuse; viscidium broadly elliptic, 0.12 by 0.09 cm, with slightly erose margins. Fruit not seen.
(after Schuiteman & de Vogel, 2009)

Colours:

Flowers white, somewhat translucent. Lip with a grass-green blotch that covers the apical half of the blade and part of the front side of the spur. Anther pure white.

Habitat:

Epiphyte in rainforest on thin branches in the canopy layer. Forest on limestone bedrock overlain with 1 to 2 m of red clay-like soil. Altitude 350–850 m.

Distribution:

Malesia (New Guinea)

Distribution New Guinea:

Papua New Guinea (West and East New Britain Prov.); see map

Cultivation:

Warm growing epiphyte.

Flowering time in the wild:

In cultivation in Hortus botanicus Leiden May–July.

Classification:

Family Orchidaceae
Subfamily Epidendroideae
Tribe Vandeae
Subtribe Aeridinae
Genus Hymenorchis
Species Hymenorchis tanii

Notes:

Hymenorchis tanii is easily distinguished by the leaves having smooth or at most slightly rough, instead of distinctly serrate margins, and the papillose-hairy ovaries. In the shape of the flowers it resembles H. serrata Schltr., but that species has a lip with serrate margins, among other differences. All other known species of Hymenorchis have relatively much broader sepals and petals.