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The diversity of the flora of Vietnam 14. Symphorema Roxb. and S. involucratum Roxb., a new genus and species occurrence for the flora

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As part of the preparation of a documented and annotated Checklist and Atlas of the Seed Plants of Cuc Phuong National Park, intensive field expeditions were undertaken to collect herbarium specimens in various habitats and locations inside the Park. During a field trip to Choi valley of the Cuc Phuong National Park (20017’52’’N, 105034’29’’ E, ca. 200 m a.s.l.), Thanh Yen municip., Thach Thanh distr., Thanh Hoa prov. on April 17, 2002, Nguyen Manh Cuong, Mai Van Xinh & Nguyen Huy Quang collected a series of interesting specimens belonging to the family Verbenaceae (NMC 1618, duplicates are kept in CPNP, HN and F). Specimens of this collection number were later identified by us as Symphorema involucratum Roxb. Not only does Symphorema involucratum represent a new occurrence for the flora of Vietnam, it also establishes the occurrence of the genus Symphorema Roxb. in the country.

Symphorema Roxb. is characterized as follows: Large scandent shrubs; hairs stellate; leaves opposite, simple, margin entire or irregularly serrulate; inflorescences capitate, subtended by a whorl of 6 prominent involucral bracts, accrescent in fruit, borne on a long peduncle; calyx 5- or 6-dentate; corolla white, small; tube cylindric, lobes 6-16 (-18); stamens as many as the corolla-lobes; ovary 2- or imperfectly 4-locular; ovules 2 per locule, pendulous, only 1 fertile; style filiform, shortly bifid; capsule indehiscent, included within an enlarged calyx, 1-seeded; cotyledons fleshy, usually with abundant oil. This genus has three species. Symphorema polyandrum Wight is endemic to India, S. luzonicum F. Villar is endemic to Philippines, while S. involucratum Roxb. has a wide range of distribution, from India, Sri Lanka, Myanmar, Thailand, China, and now found in Vietnam.

Symphorema involucratum Roxb. is characterized as follows: A vine, with young branchlets, upper surface of young leaf blade, petiole, peduncle of the inflorescence and infructescence, young involucral bracts, and outer surface of calyx densely stellate-tomentose, dull white; branchlets terete, less than 1.5 mm diam. in cross section; leaf blade subelliptic to ovate, abaxially densely stellate tomentose even when old, base largely cuneate or rounded, margin subentire to irregularly serrulate-dentate on upper part; leaves of flowering branchlets are much reduced; peduncle slender, ca. 0.4 mm diam. and ca. 2 cm long; involucral bracts spathulate, ca. 1.2 x 0.4 cm, accrescent in fruit; calyx 4-5 mm, inside glabrous; corolla white, glabrous, 6-8 mm long, lobes 6-8, narrowly oblong, 2-3 mm long; infructescence peduncle slender, up to 3-4 cm long; fruit subglobose, 4-6 mm across; involucral bracts in fruit reticulate-membranous, up to 2.5-3 x 0.8-1 cm.

In Cuc Phuong National Park Symphorema involucratum is found scattered in secondary, open, evergreen, tropical broad-leaved scrubs and woodlands, on lowland shaly hills. This Park is located in northern Vietnam, in the monsoon tropical climate with a mean annual temperature of about 230 C and a mean annual total precipitation of about 1,900 mm. The climate is further described as having a cold winter of 3 months (Dec, Jan and Feb), when mean monthly temperatures fall below 170 C, coinciding with a dry period of 4 months (Dec, Jan, Feb and Mar), when mean monthly total precipitation is less than 50 mm, followed by heavy summer rains. Flowering time is Mar-Apr, with fruits ripening probably in Aug-Oct. In China this species is found in southern Yunnan, near the border with Laos, at the elevation of 500-800 m a.s.l., in secondary scrubs and woodlands.

Le Kim Bien, Nguyen Tien Hiep
Institute of Ecology and Biological Resources
Phan Ke Loc
College of Sciences, Vietnam National University &
Institute of Ecology and Biological Resources
Nguyen Manh Cuong
Cuc Phuong National Park
Djaja Djendoel Soejarto
University of Illinois at Chicago & The Field Museum, Chicago

(Genetics and Applications, No3 2003)

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