Gastrochilus balangshanensis Jun Y. Zhang, B. Xu & Yue H. Cheng 2024, sp. nov.

Gastrochilus balangshanensis Jun Y. Zhang, B. Xu & Yue H. Cheng sp. nov. Figs 2 A, B, 3 Type. China • Sichuan: Wenchuan, Balangshan, Yinchangou, mixed coniferous forest, on tree branches, elev. ca. 2,260 m, in flower, 19 April 2023, Jun-Yi Zhang & Yue-Hong Cheng ZJY 185 (holotype: CDBI!; isotype: KUN!). Diagnosis. Gastrochilus balangshanensis is most similar to G. affinis, but can be distinguished by its shorter stem (1.5–3.5 vs. 3.0–12.0 cm), nearly elliptic leaves (vs. oblong-lanceolate to subspathulate), larger sepals (5.6–6.4 × 4.8–5.2 vs. 3.0–5.0 × 1.0– 1.3 mm) and petals (5.0–5.8 × 4.0–4.4 vs. 3.0–4.0 × 1.0– 1.3 mm), reniform epichile (vs. subtriangular) and sub-hemispherical hypochile, obtuse-rounded at the apex (vs. hypochile obconical, subacute to obtuse and shortly bifid at apex). Description. Epiphytic herb, monopodial, pendent, 1.5–3.5 cm tall. Roots vermiform, 4.0–6.0 cm long, ca. 1.6 mm in diameter. Stem unbranched, 0.5–2.5 cm long, ca. 1.5 mm in diameter. Leaves closely alternate, nearly elliptic, 0.9–1.5 × 0.4–0.8 cm, apex acute and with 1–2 lobules, lobes setaceous, with purplish-red spots. Inflorescence a raceme with 1 or 2 flowers; peduncle curved upward and thickened, 5.0–8.0 mm long, proximally covered with one sheath; floral bracts ovate-lanceolate, 0.8–1.2 cm long, apex acute. Flowers spreading, ca. 1.0 × 1.4 cm, pedicel and ovary connate, 6.0–9.0 mm long, sepals and petals heterochromatic on both surfaces, yellow-green with purplish-red spots on the outer side, purplish-red with yellow-green margin on the inner side. Dorsal and lateral sepals similar and equal in size, elliptic, 5.6–6.4 × 4.8–5.2 mm, apex obtuse. Petals oblong, 5.0–5.8 × 4.0– 4.4 mm, apex acute, base narrowed. Labellum with a reniform epichile, revolute, white with purplish-red spots, 10.0–12.0 × 5.5–6.5 mm, margin erose, smooth and glabrous above, central thickened purple-red mat with two inconspicuous ridges; hypochile sub-hemispherical, yellowish-green with purplish-red spots, 6.0–8.0 × 5.8–7.5 mm, dorsally compressed, obtuse-rounded at the apex. Column cylindrical, ca. 1.5 mm long; viscidium yellow, ca. 0.7 × 0.4 mm; stipe white, ca. 1.1 mm long; anther cap purplish-red, ca. 1.5 × 1.3 mm, rostellum bilobed, lobes acuminate at the apex; pollinia 2, ca. 0.5 × 0.4 mm, yellow, subglobular, porate; stigma deeply sunken, inverted V-shaped, ca. 0.7 mm long, yellow. Capsule ellipsoid, 12.0–15.0 × 8.0–10.0 mm, green with sparse purplish-red spots, prominently 6 - ribbed. Distribution and habitat. Gastrochilus balangshanensis is currently known only from Yinchanggou, Balang Mountain, Wenchuan County, Sichuan Province, Southwest China, part of the Hengduan Mountains (Fig. 4). It is epiphytic on tree trunks or branches in subalpine mixed coniferous forest dominated by Abies fargesii var. faxoniana (Rehder & E. H. Wilson) T. S. Liu, at an elevational range between 2200–2300 m, co-occurring with two terrestrial orchids, Goodyera recurva Lindl. and Calanthe arcuata Rolfe. Phenology. Flowering from March to April, during the dry season, fruiting from May to September. Etymology. Its specific epithet refers to the Balang Mountain, type locality of this new orchid. A Chinese name, “ ba lang shan peng ju lan ” (巴朗山盆距兰), is suggested here. Additional specimens examined. China • Sichuan: Wenchuan, Balangshan, Yinchangou, mixed coniferous forest, on tree trunk, elev. ca. 2300 m, in flower, 19 April 2023, Jun-Yi Zhang & Yue-Hong Cheng ZJY 186 (CDBI!); ibid. loc., mixed coniferous forest, on tree branch, elev. ca. 2315 m, in fruit, 22 July 2024, Jun-Yi Zhang & Yue-Hong Cheng ZJY 204 (CDBI!). Examined specimens of Gastrochilus affinis. India • Arunachal Pradesh: Lachong Valley, elev. ca. 2438 m, in flower, July 1897, R. Pantling 444 (lectotype K). China • Xizang: Chayu, under forest, elev. ca. 2685 m, in flower, 24 August 2009, Southeast Tibet Expedition Team SET-ET 717 (PE); China • Yunnan: Fugong, Jiakedi, east slope of Gaoligongshan, epiphytic on trunk, elev. ca. 2555 m, in flower, 16 May 2005, X. H. Jin 6984 (PE). Examined specimens of Gastrochilus bernhardtianus. China • Yunnan: Lijiang Prefecture, Yulong County, Yunshanping, elev. ca. 3308 m, in cold-temperate, evergreen conifer forest, in flower, 20 May 2020, J. - D. Ya et al. 20 CS 19022 (holotype KUN). Examined specimens of Gastrochilus heminii. China • Sichuan: Wenchuan, Wolong, mixed coniferous forest, on tree trunk, elev. ca. 2640 m, in flower and fruit, 15 March 2022, Min Liao & Yue-Hong Cheng ZJY 143 (holotype CDBI!); Wenchuan County, Wolong, mixed coniferous forest, on tree trunk, elev. ca. 2640 m, in flower, 14 April 2022, Min Liao, Jun-Yi Zhang & Yue-Hong Cheng ZJY 167 (CDBI!).