The Genus Alpinia Roxb. is the largest in the Zingiberaceae with about 250 species^[1]. It occurs throughout tropical Asia to subtropical Asia (Sri Lanka and the West Ghats of India to China, Japan, Southeast Asia, New Guinea, Australia as far south as the New South Wales, and the Pacific Islands as far east as Samoa ^[2-3].

In Vietnam, so far more than 30 species of this genus have been recorded^[4-7]. During a field investigation to Bac Kan, two specimens of an unusual Alpinia species (Q. B. Nguyen & X. D. Vu SH 83 and Q. B. Nguyen & X. D. Vu SH 84) were collected. Detailed studies revealed that they did not match with any of the species so far reported from Vietnam. After examining all Alpinia species from neighboring countries, we found that this species is identical to A. coriandriodora D. Fang, which was previously recorded only from Guangxi, China^[8-9]. Therefore, a new distributional record of A. coriandriodora and an addition to the Zingiberaceae flora of Vietnam are presented in this study.

Alpinia coriandriodora D. Fang, Acta Phytotax. Sin. 16(4): 79, 1978. Type: China, Guangxi Zhuang Autonomous Region, Longzhou County, Xiadong Town, (transplanted in the Medicinal Plant Garden, Nanning City), 8 April 1978, D. Fang 78908 (holotype GXMI [barcode GXMI050954]!), isotypes GXMI [barcode GXMI050955, GXMI050956]). (Fig. 1).

(Fig. 1)

Fig. 1 Alpinia coriandriodora. A: Inflorescence; B: Leaf; C: Ligule; D: Rhizome; E: Flower; F: Stamen; G: Fruit; H: Dissection of flower (from left to right): calyx, three corolla lobes, labellum, filament and anther, ovary and epigynous glands, style, stigma. From Q. B. Nguyen & X. D. Vu SH 83 and Q. B. Nguyen & X. D. Vu SH 84 (Photos: A, C-F, H by Q. B. Nguyen; B, G by X. D. Vu)

Perennial herb, 80-150 cm high, clump-forming, with strong smell. Pseudostem slender, 6-10 mm in diameter; leaf blade elliptic-lanceolate, 13-16 cm× 2.5-3.3 cm, base cuneate, apex long caudate, cauda 2-4 cm long, glabrous; petiole 3-6 mm long; ligule bilobed, 3-5 mm long, margin ciliate, apex rounded. Leaf sheath glabrous. Inflorescence 5-10 cm long, rachis puberulent; bracts lanceolate, light green, 8-10 mm long. Flowers 2-4 per cincinnus, usually only 2 of them fertile; pedicel 1-1.5 mm long, pubescent; flower small; calyx tubular, 7-9 mm long, outer surface puberulent, split down to 1.5-2 mm on one side, apex shallowly trilobed, tip acute; floral tube 5-7 mm long, light red-brown; dorsal collora lobe oblong, light green, 5-7 mm long, 3-4 mm wide, apex cucullate, margin often ciliate; lateral corolla lobes slightly narrower than dorsal one, labellum light yellow with red-brown stripes, 5-6 mm×3-3.5 mm, stripes radiate from the middle to the margin; lateral staminodes linear, 3-6 mm long, filament oblong, 5-6 mm long, 2-3 mm wide, ca 1 mm thin, red-brown, pilose adaxially; anther curved when flowering, 3-4 mm long, ca 3 mm wide; anther crest triangular, entire, ca 1 mm long, ca 1.5 mm wide; style filiform, white, stigma cylindrical, slightly narrowed at base, margin ciliate; epigynous glands oblong, ca 2 mm long. Ovary cylindrical, 1-1.5 mm long, ca 1 mm in diameter, green. Capsules globose, 0.8-1 cm in diameter, red when mature; seeds light brown, aril white, membranous.

Distribution: Vietnam (Bac Kan), China (Guangxi).

Habitat and ecology: This species often grows in forest of limestone hills. It occurs at 230-860 m a.s.l.

Phenology: Flowering in April-June and fruiting in July-November.

Vietnamese name: Gừng đá.

Notes: Alpinia coriandriodora is the most similar species to A. bambusifolia in general habit, cincinnate inflorescences, but differs from the latter in having elliptic-lanceolate leaf blade, light yellow labellum with red-brown stripes and triangular anther crest (vs. narrowly lanceolate leaf blade, white labellum with red stripes and without anther crest) (Table 1).

(Table 1)

Table 1 Morphological comparison of Alpinia coriandriodora and A. bambusifolia A. coriandriodora A. bambusifolia Leaf blade Elliptic-lanceolate, 13-16 cm×2.5-3.3 cm Narrowly lanceolate, 3-25 cm×0.7-3.5 cm Calyx Light yellow from base to middle and purple-red from middle to apex, 7-9 mm long Pale purple-red, 9-11 mm long Labellum Light yellow with red-brown stripes, 5-6 mm×3-3.5 mm White with red stripes, ca 9 mm×6 mm Anther crest Triangular, entire, ca 1 mm long, ca 1.5 mm wide Absent Fruits Globose, 8─10 mm in diameter Cylindrical, 1-1.5 mmlong, 0.5-0.9 cm in diameter

Table 1 Morphological comparison of Alpinia coriandriodora and A. bambusifolia

Additional specimens examined: Vietnam. Bac Kan Province: Na Ri District, Liem Thuy commune, 860 m a.s.l., 21°58'14.7" N, 106°05'09" E, 07 April 2016, Q. B. Nguyen & X. D. Vu SH 83 (VNMN, IBSC); ibid., 860 m a.s.l., 21°58'03.2" N, 106°02'52.6" E, 11 April 2016, Q. B. Nguyen & X. D. Vu SH 84 (VNMN, IBSC).

China. Guangxi Zhuang Autonomous Region: Longzhou County, Xiadong Town, (transplanted in the Medicinal Plant Garden, Nanning City), 8 April 1978, D. Fang 78905 (GXMI [barcode GXMI050958, GXMI050958]); ibid., 7 May 1979, D. Fang & D. H. Qin 78917 (GXMI044623); ibid., 4 May 1967, Y. X. Gan 5098 (GXMI044624); ibid., 3 April 1961, W. G. Lu 20512 (GXMI044625), Guilin City, Yongfu County, Baishou Town, Sanhe Village, H. Z. Ye et al. 46716 (GXMI044626); ibid., 230 m a.s.l., 13 September 1974, C. Z. Gao & D. Fang 46673 (GXMI044622, GXMI044627).

Acknowledgments we would like to express our gratitude to the curators of the GXMI, IBSC, VNMN herbaria for allowing us access to herbarium material.