Gastrodia Brown^[1](Gastrodieae, Epidendroideae) is the largest genera of non-photosynthetic mycohetero- trophic orchids. It, so far, consists of approximately 80 accepted names^[2] and is considered to comprise ca. 90 species^[3-4]. The genus is characterized by underground fleshy tubers, lacking of functional leaves and chlorophyll, fusion of the sepals and petals and two mealy pollinia without caudicles^[5-7]. It is widely distributed throughout the temperate and tropical regions of Asia, Oceania, Madagascar and Africa^[7-9]. Southeast Asia is the modern distribution center of the genus with 24 existing species^{[2, 10-11]}. China and Australia are another two diversity hotspots with 20^{[9, 12-16]} and 15 species^[17], respectively.

As most of the life cycle being underground, a relatively short blooming period and small scattered populations, Gastrodia species can only be discovered when flowering or fruiting^[18], which lead to few orchid-collecting expeditions have coincided with Gastrodia's blooming periods. The authors are lucky to find a species of Gastrodia during a floristic survey in Guangdong. After careful morphological comparison with its close relatives^{[9, 14, 19]} and other species of Gastrodia recorded in China, we confirmed it is conspecies with G. albida T. C. Hsu & C. M. Kuo^[14] from Taiwan, China. We thus report the first known occurrence in mainland China, which makes the number of Gastrodia species reach to 11 species in the area. A detailed description, illustration and ecological information are presented herein.

Gastrodia albida T. C. Hsu & C. M. Kuo, Ann. Bot. Fenn. 2011, 48(3): 272-275. Type: China. Taiwan, Taipei County, Wulai Township, Pataoerhshan, 800 m alt., 12 Jun. 2008, T. C. Hsu 838 (holotype TAI; isotype TAIF). (Fig. 1)

Terrestrial, achlorophyllous herbs. Roots few, slender. Rhizome tuberous, fusiform, 1.5-5 cm long, grayish brown, hairy and covered with numerous scales. Scales verticillate, lanceolate, pale yellowish brown, 1-2 mm long. Inflorescence a terminal raceme, erect, 1-5 cm long; Peduncle straight or slight fle- xuose, 3-4 noded, with 2-3 tubular, membranous sheaths, 2-8 cm tall; rachis less than 5 mm long. Floral bracts membranous, ovate to ovate-oblong, pale brownish, 2-6 mm×1.5-4 mm. Pedicel and ovary 5-25 mm long, ovary 2-2.5 mm in diameter. Flowers 2-8, white, erect, bell-shaped, obovate in dorsal view, not widely opening, 4-7 mm in diameter. Sepals and petals united, forming a 5-lobed perianth tube. Sepals fleshy, thickened, 9-15 mm long, connate with each other for 1/5-1/6 of their length and with petals for more than 4/5 of their length, whitish on both surfaces, outside top distinct verruculose or sometimes lightly verruculose to nearly absent, apex incurved, brownish tinged; free portion of dorsal sepal semi-orbicular. Petals connate with sepals, located near the sinus between dorsal and lateral sepals, free portions brow-nish, ovate-oblong, connate portions distinctly thickened and tinged orange-yellow inside, forming a pair of ridge-like structures inside perianth tube. Lip free from floral tube, white tinged orange-yellow at base and reddish at apex and margin, 3.5-4 mm×2.2-2.5 mm, hypochile with two whitish, globose, subsessile, nectarless calli, ca. 1 mm in diameter; epichile elongated-deltoid, disc thickened and 2-ridged in middle, the ridges higher and tinged grayish-green near apex. Column white, straight, stout, 4-4.5 mm× 1.8-2 mm, with a pair of lateral wings distally; edges of lateral wings parallel to column, tips superior to anther; column foot very short or absent; rostellum and clinandrium lacking; stigma round, located near base. Anther hemispheric, 0.6-0.8 mm long, pollinia 2. Capsule ellipsoid, 1-1.7 cm long; pedicel elongating to 15-30 cm long in fruit. Seeds fusiform. Fl. May to early June, fru. May to June.

Additional specimens examined: CHINA: Guangdong: Huizhou City, Longmen County, Nan-kunshan Nature Reserve, along the road at the foot of mountain, 565 m altitude, 14 May 2013, Tong Yi 13051455 (IBSC); Zhaoqing City, Fengkai County, Heishiding Nature Reserve, under broad-leaved forests mix with bamboo forest, ca. 570 m altitude, 31 May 2013, Tong Yi et al. 13053129 (IBSC).

Habitat and ecology: Under broadleaved forests mix with bamboo forest or secondary broadleaved forests. Flowering from May to early June and fruiting from May to June.

Distribution: Restricted in Guangdong and Taiwan, China.

Notes: The Gastrodia albida complex (G. albida T. C. Hsu & C. M. Kuo, G. albidoides Y. H. Tan & T. C. Hsu and G. theana Averyanov^[19]) are easily distinguished by dwarf habits, whitish and scarcely opening flowers, curved and fleshy perianth tubes, hardly connate lateral sepals and a relatively short column and lip from the Gastrodia congeners.

Averyanov, in 2005, firstly published Gastrodia theana from Vietnam distinguished by perianth tube with distinctly striate and verrucose throughout, cordate based lip and a well-developed rostellum^[19] (shown in Averyanov 2005: Fig. 6g^[19] and Averyanov 2011: Fig. 43^[20], although not described in the text^[19]). Hsu & Kuo, in 2011, published G. albida from Taiwan Island characterized by its perianth tube with mode- rately verrucose throughout and without striate outside, larger free portions of the petals, truncate based lip and absence of a rostellum^[14]. Hsieh's et al., in 2012, report the new record species of G. theana in Taiwan, China^[21], which was actually the misidentification of G. albida according to the description of "actually lacking in rostellum" and perianth tube with dorsal "longitudinal grooves" (Hsieh et al. 2011: Fig. 3)^[21]. Tan et al., in 2012, published G. albidoides from Yunnan, China, distinguished by an almost smooth perianth tube, moderately free portions of the lateral sepals, un-thickened petals, absence of a rostellum (shown in Tan et al. 2012: Fig. 1B & C^[9], although "a well-developed rostellum" described in the text) and distinct column foot^[9].

Within the Gastrodia albida complex, differences between them are subtle, especially G. albida and G. albidoides. Morphologically, Gastrodia albidoides differs G. albida by the slightly verrucose toward apex, otherwise smooth perianth tube (vs. distinctly verru- cose throughout in later), lateral sepals adnate to 1/2 their length (vs. adnate to 1/5-1/6 their length), petals thin in texture (vs. fleshy), lip rounded at base (vs. truncate at base), distinct column foot (vs. either absent or obscure). Our comprehensive morphological studies of the two populations from Guangdong indicated that their key character (e.g. lip truncate at base and the absence of column foot) are well identical with G. albida. What is slightly different from the type of G. albida is the number of wart on perianth tube between them (perianth tube slightly verrucose toward apex or otherwise smooth in former vs. distinct verrucose outside in later). Considering the number of wart on perianth tube should be an unstable quantitative character, herein we report the new record species of G. albida from mainland China. However, the morphological differences between the two species need to be further studied. The "distinct column foot" described and presented in the original material of G. albidoides was actually not that "distinct". The lip base seems easily transitional from round to truncate. The "smooth perianth tube" of G. albidoides, the "slightly verrucose toward perianth tube apex" of the two population present here and the "distinctly verru- cose perianth tube throughout" of G. albida, seems to form a continuous variation.

Acknowledgments The author would like to thank the anonymous reviewers for their valuable comments and suggestions on the manuscript, and the staff in Heishiding and Nankunshan Nature reserves, for their assistance in the field.