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The diversity of the flora of Vietnam 15. Phyllocyclus Kurz and P. lucidissimus (H. Lév. & Vaniot) Thiv (Gentianaceae), genus and species new to the flora

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Recent collections made in Ha Long Bay, Quang Ninh Province included specimens (Trinh Nu cave, 20050'20''N, 107006'08''E, near sea level, Nguyen Tien Hiep NTH 4049, 09.11.1999; Ang Du, 20047'36''N, 107008'04''E, on slope of limestone mountain about 40 m a.s.l., Nguyen Tien Hiep et al. NTH 5867, 19.07.2003; Trang Luoi liem, 20050'32''N, 107010'11''E, near sea level, Nguyen Tien Hiep et al., s.n., 10.07.2003) of an interesting plant in the family Gentianaceae. They were identified at first as C. lucidissima (H. Lév. & Vaniot) Hand.-Mazz., a species not known yet in Vietnam. Most taxonomists (A. Ubolcholaket, 1987; T.N. Ho et al., 1988; Pham Hoang Ho, 1993; D.J. Mabberley, 1993; T.N. Ho & J.S. Pringle, 1995) treated Canscora Lam. in the broad sense (sensu lato). Based on recent molecular phylogenetic analysis, a narrower definition (sensu stricto) of Canscora Lam. was suggested. Phyllocyclus Kurz once reduced to subgeneric rank in the classification of Canscora Lam., s.l. by C.B. Clarke (1885), was re-established by Thiv (2003). Two new combinations (Phyllocyclus lucidissimus (H. Lév. & Vaniot) Thiv and P. petelotii (Merr.) Thiv. were made accordingly. In this paper we accepted Thiv's genus and species concepts. Therefore Phyllocyclus Kurz and P. lucidissimus (H. Lév. & Vaniot) Thiv are new occurrences in the flora of Vietnam.

Phyllocyclus Kurz are annual or perennial, erect, glabrous herbs. Leaves opposite; basal cauline leaves free; cauline leaves perfoliate, orbicular as bracts. Inflorescences axillary, few-flowered, lax cymes. Flowers (except calyx) pentamerous, mostly sessile, without bracteoles. Calyx penta- or tetra- merous, inflated, urceolate or tubular. Corolla actinomorphic, urn-, funnel- to salver- shaped, white-yellow to cream-coloured; tube longer than lobes. Androecium isomorphic or anisomorphic with filaments of different lengths; stamens inserted equally in corolla tube; filaments broadened at the base. Ovary ovate to obovoid; stigmatic lobes rounded. Fruit a septicidal capsule with numerous seeds. Five species, all of mainland SE Asia distribution (Myanmar- 2 species, Thailand- 1, Laos- 2, southern China- 1 and northern Vietnam- 1). Very rare, commonly on limestone areas.

Phyllocyclus lucidissimus (H. Lév. & Vaniot) Thiv is a perennial herb, 0.1-0.3 m tall, with woody base of stem and rootstock. Basal cauline leaves spatulate or obovate, apex rounded, c. 1.5 cm x 0.9 cm; cauline leaves 1.2-2.6 cm x 2.1-3.2 cm; leaves and bract venation reticulate, prominent on both surfaces. Inflorescences axillary, 3- to 12- flowered, lax cymes (mostly dichasia); bracts orbicular, funnel shaped, 5-8 mm x 11-13 mm. Flowers sessile. Calyx tetra- or penta- merous, inflated, urceolate; tube 4-5 mm long; lobes triangular, 1.5 mm by 1.5 mm. Corolla urn- to salver- shaped, 5-6 mm by 3 mm, white or pale yellow; lobes oblong-spatulate, 2.5 mm x 1 mm. Androecium isomorphic, filaments of equal length, filiform, c. 3 mm long. Ovary ovate or oblong, surface constricted; style filiform, up to 4 mm long. Capsule oblong or ovate, 3.5 mm by 2 mm. Seeds brownish, ovate, c. 0.3 mm by 0.25 mm; outer testa reticulate, with shallow cells. This species is distributed in southern China (Guizhou and Guangxi) and northern Vietnam (only in sites cited above). This area has monsoon tropical climate with winter of 3 cold and 5 dry months and summer rains. Plants grow on rich soils in humus crevices on limestone rocks, cliffs and slopes near sea level, and bear old flowers and young fruits in November, while in China they grow at higher elevations, 1000-1600 m and bloom in March, August.

Hình 1- Phyllocyclus lucidissimus (H. Lév. & Vaniot) Thiv Cỏ xuyên lá bóng 1. Cây mang hoa già và quả non; 2. Lá trên thân; 3. Lá hoa; 4. Lá hoa (mở một phía) và hoa già; 5. Bộ nhị cái. Bùi Xuân Chương vẽ theo Nguyễn Tiến Hiệp NTH 4049.

Le Kim Bien, Nguyen Tien Hiep
Institute of Ecology and Biological Resources
Phan Ke Loc
University of Sciences, VNU & Institute of Ecology and Biological Resources
Pham Van The
College of Forestry

(Genetics and Applications, No1 2004)

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