Gastrochilus corymbosus A.P. Das & Chanda (1988: 401)

Liu, Qiang, Zhou, Shi-Shun, Li, Ren, Tan, Yun-Hong, Zyaw, Myint, Xing, Xiao-Ke & Gao, Jiang-Yun, 2020, Notes on the genus Gastrochilus (Orchidaceae) in Myanmar, PhytoKeys 138, pp. 113-123 : 113

Gastrochilus corymbosus A.P. Das & Chanda (1988: 401) Figure 2

Type.

INDIA. Jalapahar, Darjeeling (West Bengal), about 2200 m a.s.l., epiphytic on tree trunks. 29 Oct 1982, A.P. Das 823 (holotype: CAL!)

Description.

Epiphytic pendulous herb. Stem often branched, pendulous and usually 8.0-15.0 cm long with 0.4-0.5 cm internodes. Leaves distichous, blade oblong or falcate-lanceolate, 2.0-4.0 × 0.4-0.9 cm, apex acute and unequally 2-lobed. Inflorescence corymb, 4-6-flowered; peduncle 1.2-1.3 cm, upper part broader, lower part with 2 cupular sheaths with purple-red spots; floral bracts ovate-triangular, ca. 3.0, membranous; pedicle and ovary yellow-green with purple-red spots, 1.0-1.2 cm long. Flowers yellowish or yellow, with purple blotches; epichile of lip white with sparse purple spots. Dorsal sepal oblong-elliptic, concave, 5.0-6.5 × 3.6-4.5 mm, apex obtuse; lateral sepal similar to dorsal sepal, 6.2-6.5 × 3.2-4.0 mm, apex obtuse; petals sub-obovate, 5.5-6.5 × 3.5-4.2 mm, apex rounded. Lip with distinct partition between wide epichile and a saccate hypochile; epichile reniform, 4.0-4.9 × 8.0-9.0 mm, adaxially glabrous, with a slightly diamond-shaped central cushion covered with small brown spots and 2 conic calli near base, margin entire or slightly denticulate, emarginate at apex; hypochile cupular, laterally compressed, 7.2-7.8 mm tall, 5.8-6.2 mm in diameter, apex rounded. Column stout densely with purple spots, ca. 2 mm; anther cap galeate with recurved acuminate apex, 2.0 × 2.2 mm; pollinia 2, ca. 1.0 mm in diam.; stipe elongate, ca. 2.0 mm; rostellum bilobed with acuminate apex. Capsules cylindrical with 3 ridges, ca. 2.0 × 1.2 cm.

Phenology.

Flowering occurs in April to October.

Distribution and habitat.

Gastrochilus corymbosus is previously only known from the India and this is the first time that it has been recorded in the Natma Taung (Mt.Victoria) National Park, Chin State, Myanmar. It was found growing as an epiphyte on the tree trunks in a Rhododendron forest, which is dominated by Rhododendron protistum var. giganteum (Forrest) D.F. Chamberlain.

Additional specimens examined.

MYANMAR. Chin State. Natma Taung (Mt. Victoria) National Park, 2750 m a.s.l., epiphyte on the trunk of Alpine Rhododendron forests, 9 Jan 2017, Qiang Liu 414 (HITBC!). Natma Taung (Mt.Victoria) National Park, 2900 m a.s.l., epiphyte on the trunk of Alpine Rhododendron forests, 30 Apr 2017, Yun-Hong Tan M1271 (HITBC!).

Note.

Only a single specimen and illustration of this species previously existed, on which the original description was based ( Das and Chanda 1988). Foliar and floral characteristics were not described in sufficient detail in the original description, due to the extremely poor state of the preserved specimen and it was not possible to conduct a detailed study on this species. Now that fresh material has become available, a detailed description of the species has been provided here. On the basis of the long and pendulous stem, G. corymbosus can be placed in section Microphyllae ( Tsi 1996). This species exhibits great variation between populations in leaf shape from falcate-lanceolate to oblong (Figure 2 C ). Morphologically, it shows a close affinity to G. distichus (Lindley) Kuntze, but differs from the latter by having much shorter (less than 15 cm) and stout stem, apex of leaf unequally 2-lobed without awns, inflorescences corymb with 4-6-flowers, epichile of lip with a slightly diamond shaped central cushion, margin entire or slightly denticulate, emarginate at apex ( Das and Chanda 1988; Chen et al. 2009).

Figures

Figure 2. Gastrochilus corymbosus A, B habitat C plant D leaf E front and lateral view of flower F sepals and petals G anther cap H pollinarium I fruit.