DIVERSITY OF THE FLORAOF FAN SI PAN, THEHIGHEST MOUNTAIN INVIETNAM'Nguyen Nghia Thin2 andDaniel K. Harder"ABSTRACT Fan si Pan, situated in northern Vietnam near the border with China and reaching an altitude of 3143 m, is thehighest mountain in Vietnam. The flora of this mountain and surrounding region is rich. containing a mixture ofsubtropical and temnperate components. It also supports many relictual plant species that possibly represent remnantextensions of the old. subtropical flora of the southern Yunnan Province of China. The flora is diverse and characterizedby the following: Aceraceae (Acer); Cupressaceae (Fokienia hodginsii (I)umm) Henry & Thomas); Ericaceae (Rhodo-dendron, Vacciniunm): Fagaceae (Castanea. Castanopsis. Fagus. Lithocarpus. Quercus); Juglandaceae (Carya, Engelhar-dia, Juglans, Platycarya); l.auraceae (Beilschmiedia. Machilus, Phoebe, Neoliswea); Magnoliaceae (Liriodendron, Mag-nolia. Manglietia. Michelia); and Pinaceae (Ahies nukiangensis Cheng & 1.. K. Fu, Tsuga chinensis (Franch.) Pritz). Fan si Pan, located at 22�09'-23�30'S, 103�-103�59'E and reaching an altitude of 3143 m, is the highest point in Vietnam. It is situated in the mountainous northwest province of Lao Cai. Fan si Pan and its contiguous mountain range are oriented along the Red River in roughly a northwest to southeast direction and extend into the Yunnan Province of China and to the Himalayan chain to the northwest. This range of mountains is derived from rocks of gneiss and ancient granite. The cli-mate is humid or perhumid (76-96%) year-round with an average yearly rainfall of 2770 mm; the heaviest rains are concentrated in the months of July and August. The average temperature is about 15�C, with a range between -3�C and 20�C. De-cember and January are the coldest months, when snow can fall for 1-3 days each year. This paper presents a listing of plant species from this diverse region of Vietnam, discusses the main vegetation types occurring there, and relates the Sino-Himalayan affinities of specific taxa to past climatic shifts believed to have occurred in this region. FLORISTIC DivEisrry On the basis of published works by Lecomte(1907-1951), Vo Van Chi (1975), Aubreville et al.(1960-1983). Ke et al. (1969-1976), Ho (1970-1972, 1991-1993) and Loe (1984), and resultsfromn our preliminary investigations (1991-1992),the flora of Fan si Pan is reported and arrangedaccording to the Brunmmitt (1992) system, including1750 species belonging to 680 genera in 210 fam-illes of 7 divisions as presented in Table 1. Table 2 shows that in only 22 families, 746 spe-cies, or 43% of the total species found on Fan siPan, are represented. There are several widespreadand well-known families with abundant taxa rep-resented in the flora. The mnost significant of theseinclude the Orchidaceae (26 genera and 62 spe-cies), Asteraceae (36 genera and 59 species), Eri-caceae (6 genera and 58 species), Poaceae (30 gen-era and 47 species), and Cyperaceae (6 genera and42 species). In the Fan si Pan flora there are also many spe-ties-rich genera with a large number of taxa. Thesegenera are listed in Table 3. Table 3 shows that in only 26 genera, repre-senting 3.8% of the 680 known genera in the re-gion, the 388 species comprise nearly 22% of thetotal in the flora, suggesting that the region aroundFan si Pan and the local conditions have selectivelyencouraged diversification in several genera. A diversity of morphologies are found in the flora ' The authors thank Vo Van Chi, College of Pharmacy, IHo Chi Minh City, Vietnam, and G. T Prance. Director ofthe Royal Botanic Gardens, Kew, U.K., for providing valuable references. We also thank Peter Raven, Director of theMissouri Botanical Garden, U.S.A., for receiving and transmitting our manuscript to the Annals ofthe Missouri BotanicalGarden. We recognize the valuable comments and corrections to our manuscripi provided by H. van der Werff. editor,and A. Scheuler McPherson. NNT would like to recognize the support for this investigation by the Program of BasicScientific Research provided by the Vietnamese Government. 2 Herbarium, Department of Botany, Vietnam National University, 90 Nguyen Trai Road, Dong D)a, Hanoi, 10,(X0),Vietnam. : Missouri Botanical Garden, P.O. Box 299. St. Louis, Missouri 63166-0299, U.S.A.ANN. MISSOURI BOT. GARI). 83: 404-408. 1996.