Materials and methods

The description presented hereafter is based on Vietnamese material found in Khanh Son district, Khanh Hoa province, supplemented with other specimens from the senior author’s private collection, originally collected in the Daklak province, Vietnam. The measurements and description were prepared from living plants. Herbarium material was preserved in 70% ethanol and stored at VNM herbarium. All the photos were taken with a Canon 600D fitted with a EF-S 60mm f/2.8 Macro USM lens. Terminology for the morphological description follows ^{Beentje (2012}).

Taxonomic treatment

Pelatantheria woonchengii P.O’Byrne, Malayan Orchid Rev. 43: 98. 2009 (Figure 1).

Figure 1 Pelatantheria woonchengii. A, habit. B, flower in frontal view. C, flower in side view. D, flower in upper view. E, dorsal sepal. F, lateral sepals. G, petals (abaxial and adaxial views). H, labellum with spur in adaxial (1) and frontal (2) views. I, mid lobe with spur, the lateral lobes removed (1) and present (2). J, column and pedicel. K, column. L, anther cap in frontal (1) and dorsal (2) views. M, pollinarium in frontal (1) and dorsal (2) views. Photo and drawing by Truong Ba Vuong from BV 300. 

TYPE: Thailand. Cult. at Woon Leng Nursery (Singapore), O’Byrne PX450 (SING!)

Creeping epiphyte herb. Aerial roots, occasionally branched, produced along stem. Stem to over 30 cm long, slightly compressed. Leaves distichous, thick, elliptic, concave, obtuse, slightly unequally bilobed, channeled along the midvein, 2.0-2.5 × 0.9-1.0 cm. Inflorescence axillary along the stem, ca. 1 cm long, peduncle short, slightly compressed, ca. 2 mm long, covered by 3 tubular bracts; rachis thicker than peduncle 7-8 mm long, 1-2 flowered; floral bract triangular, acute, ca. 2 mm long. Flower spreading, yellow striped with red on petals and sepals, the labellum yellow, the spur greenish-yellow. Dorsal sepal ovate, obtuse, ca. 4-5 × 3 mm. Lateral sepals oblique, elliptic, sub-acute, ca. 6-7 × 3 mm, with a distinct abaxial keel along the midvein. Petals thinner than sepals, narrowly elliptic, sub-acute ca. 5 × 2 mm. Labellum 3 lobed, spurred, immobile, ca. 12 mm long (from tip of spur to tip of mid lobe); spur ca. 4 mm long, apex rounded, truncate, emarginate, slightly curved forward; lateral lobes erect, triangular, ca. 3 × 2 mm; mid lobe broadly ovate to suborbicular, rounded, the margins slightly curved forward, 6-7 × 5 mm wide, the apex with an appendage 2 mm long and tufts of white hairs on the sides of apex; provided with 3 keels continuous from the ridge of spur septum, the central one lower than the lateral keels, fused on the middle of mid lobe into one narrower keel connecting with the apical appendage; spur provided on the floor with a median ridge, create the septum of spur and dividing it into 2 halves; the sidewall callus and the callus on the floor forming a backwall, laminar, ovate, papillose, T-shaped callus ca. 1.5 mm long. Column stout, ca. 2 mm long, provided at the base with 2 tufts of white glandular hair on each side, the apex with 2 pairs of lateral stelidia, the upper two incurved, papillose, embracing the anther cap, the other two shorter, oblique. Anther cap triangular. Pollinia 4, in two pairs, subglobose. Ovary (with pedicel) 1.1 cm long, the ovary straight, the pedicel slightly up curved. Capsule not seen. (Fig. 2-3).

Figure 2 Pelatantheria woonchengii , detail of the column. Photo and drawing by Truong Ba Vuong from BV 300. 

Figure 3 Ridges on labellum of Pelatantheria woochengii. Drawn by Truong Ba Vuong from BV 300. 

Flowering Time: From mid-October to late November.

Distribution: Khanh Son district (Khanh Hoa province), Daklak, Ninh Thuan. Peninsular Malaysia (Pahang), Thailand.

Specimen examined: Khanh Son District (Khanh Hoa province) BV 239 (VNM). Daklak province, flowered in the private collection of the senior author, BV 300 (VNM). Without specific locality, Nguyen Van Khangs.n. (Photo).

Figure 4 Species of Pelatantheria. A. P. ctenoglossum Ridl. (Photo by Chu Xuan Canh) and B. P. woochengii P.O’Byrne (photo by Truong Ba Vuong). 

Pelatantheria woonchengii looks very similar to P. ctenoglossum and is misidentified in Vietnam. Below is the comparison of the two species (Table 1, Figure 4).

There are 2 flower forms of P. woochengii found in Vietnam. The first one is described above. Another form (observed in the collection of the second author) is striped with red and has a lower number of stripes (Figure 5).

Figure 5 Specimens of Pelatantheria woonchengii with fewer reddish stripes. A, photo from theprivate collection of Nguyen Van Khang; B, photo of BV 239, collected by the senior author in Khanh Son district (Khanh Hoa province). Photo by Truong Ba Vuong. 

Pelantantheria woochengii has recently been sold through the Internet in the Vietnamese market of wild orchids, at a very cheap price. Many populations of the species were destroyed by overcollection.

Artificial identification Key To The vietnamese species of Pelatantheria*

1a. Pollinia 2, without hairs on column, short and thin appendage without projection on labellum apex P. eakroensis

1b. Pollina 4 2

2a. Midlobe of labellum smooth, without projection on midlobe apex 3

3a. Midlobe with unclear central thickening, without or unclear hairs on column P. insectifera

3b. Midlobe with single mid ridge, dense white glandular hairs on column apex P. rivesii

2b. Midlobe of labellum with prominent yellow calli or warty cushion callus, with projection on midlobe apex 4

4a. Midlobe of labellum with 3 yellow calli, 2 tufts of hairs on each side of column P. woochengii

4b. A broad warty yellow callus nearly covered midlobe, 1 tuft of hairs on each side of colum P. ctenoglossum

*Based on data from ^{Seidenfaden (1992}), ^{Haager (1993}), ^{Averyanov (1994}), O’Byrne (2009), ^{Chen and Wood (2009}).