Ixora is the third largest genus of the family Rubiaceae, comprising of about 500 species (Mouly et al., 2009) and commonly distributed in tropical Africa, America, Asia, Madagascar and Pacific islands (Tao and Taylor, 2011). Thirty four taxa of Ixora are confirmed in Indochina regions (Ganepain, 1923) and twenty three species and six varieties are distributed in Vietnam (Pham, 2003).
Recently, while checking herbarium specimen of Ixora in Herbarium of the Institute of Ecology and Biological Resources (HN) Hanoi, unidentified specimen which was collected from Van Ban (Lao Cai) in 2008 was found. At the same time, the same plant was also found during our recent field work from Xuan Lien Natural Reserve, Thuong Xuan district, Thanh Hoa province (19°59′32.78″N, 105°1′18.41″E) at an elevation of 510 m (Fig. 1, Fig. 2). The plant differs from a closely related species Ixora coccinea in auriculate shape of base leaf, more number of secondary veins, shorter stipules, calyx having more number of appendices, shorter corolla tube, oblanceolate shape of corolla tip (Table 1). On the basis of available literatures (Pham, 2003; Tao and Taylor, 2011) and carefully studying a type specimen of the plant, finally it was identified as Ixora auricularis Chun & F. C. How ex W. C. Ko for the first time from Vietnam. Previously its distribution has been known only in Yunnan of China. In this study, we reported Ixora auricularis as a newly added taxon to the Flora of Vietnam and its description, habitat, color photographs, illustrations and key of related taxa are provided.
Taxonomic Treatment
Ixora auricularis Chun & F. C. How ex W. C. Ko, Guihaia 19: 99–100, 1999.—TYPE: China. Sino-Russian Exped. 2347 (SCBI).
Shrubs or small trees up to 6–10 m high. Young branches glabrous, green. Leaves opposite, sessile; blade oblanceolate, oblong elliptic, or obovate-elliptic, 10–23 × 5–9 cm, glabrous on both surfaces, base cordate-auriculate, apex shortly acuminate, drying thinly papery, brown adaxially, pale abaxially; secondary veins 10–13 pairs; stipules broadly triangular, 7–18 mm, awn of stipules 5–7 mm, seta inside. Inflorescences terminal, corymbose, 6–15 cm wide; axis pubescence; peduncle 3–5 cm, articulate near base, at articulation with reduced leaves ca. 3 cm; bracteoles linearlanceolate, ca. 1 mm; pedicels 2–3 mm. Flowers sessile or pedicellate. Calyx with hypanthium obconic, tube 1–1.5 mm; limb deeply lobed; lobes 4, ligulate, 0.5 mm long, having 6 appendices. Corolla purplish red; tube 2–3.5 cm, glabrous at throat; lobes oblanceolate-oblong, 7 × 3 mm, apex acute, sparse hair at base. Stamens 4, short filaments 1 mm; anthers 3 mm, acute at tip, bilobate at base. Ovary 2 loges, one ovule per loge; stigma bipartite. Drupe globose, 6–8 mm in diam..
Habitat: The species growing in evergreen forested.
Flowering: May–Jun.
Distribution: Vietnam (Lao Cai, Thanh Hoa), China (Yunnan).
Specimens examined: VIETNAM. Lao Cai province: Van Ban, 2008, Nguyen Quoc Binh et al. VN 1965 (VN); Thanh Hoa province: Thuong Xuan, 2016, Nguyen Dinh Hai et al. Trang-005 (VN).
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