Abstract:

 The Hengduan Mountain Region on the south-eastern fringe of the  Qinghai-

Xizang (Tibet) Plateau is located in W. Sichuan, N. W. Yunnan and E. Xizang, with a wide

area of juxtaposition from the east to the west, the mountains extending and the rivers flowing

from the north to the south.   In this paper it covers an area from Daojie, Wayao, Yingping,

Yangbi, Dali of Yunnan and Dukou of Sichuan in the south, to Banbar, Dengqeu, Shenda of 

Tibet and Serxu, Dainkog, Shuajingsi and Nanping  (Jiuzhaigou)  of Sichuan in the north,

and from Lharong, Baxoi and Zayü of Tibet in the west, to Maowen, Wenchuan, Mt. Erlang,

Mt. Emei and Xichang of Sichuan in the east (Fig. 1.). The Gongga Mountain is the highest

in the region, its summit being at an altitude of 7556m, whereas the Dadu River Valley in

the eastern part of the area is only 1150 m above sea level.  Therefore, the relative height is

about 6400 m in the region.  The Hengduan Mountain Region is well-known for its various

topography, complex natural conditions and rich flora.

       The floristic composition and features of orchids in Hengduan Mountain

Region.

       1.  The species of orchids are abundant in the region.  As we know so far, orchids in 

the Hengduan Mountain Region comprise 91 genera and 363 species with 9 varieties, and thus

it is one of concentration centres of orchids in China, making up 56.17% of the total number

of orchids genera in China, only less than in Yunnan and Taiwan, and 34.87% of the total

number of orchids species in China, only less than in Yunnan and Sichuan.

      2.  The orchids genera in the Hengduan Mountain Region are complex in geographical

components as indicated below:

       (1)  Four geneva are endemic to China and one of them is endemic to the region.

       (2)  Fourteen genera are of the north temperate distribution pattern, 2 of the Old World

temperate one, 18 of the East-Asian one (including Sino-Himalayan and Sino-Japanese) and

3 of the East-Asian-North American one.

       (3)  Twenty one genera belong to the tropical Asian distribution pattern, 3 to the tropical

Asian-tropical African one, 13 to the tropical Asian-tropical Australian one, 1 to the tropical

Asian-tropical South American one, 8 to the Old World tropical one and 2 to the pantropical

one.

     (4)  Two genera are cosmopolitan.

     The analysis of genera:   Fourty eight genera (containing 151 species with 4 varie-

ties) of the tropical distribution occur in the region, among which Calanthe and Cymbidium

distributed in the temperate region, and Bulbophyllum and Peristylus in the subtropical part

of China are comparatively abundant (with over 10 species), but the other 25 genera are mo-

nospecific and 11 genera each contain only 2-3 species.  Some epiphytic genera mainly distri-

buted in tropical Asia and belonging to tropical florestic elements, such as Vanda, Luisia,

Schoenorchis, Flickingeria, Monomeria, Kingidium,  Acampe, Phalaenopsis,   Thrixspermum,

Eria, Taeniophyllum, and terrestrial genera, such as Aphyllorchis, Collabium, Mischobulbum,

Paphiopedilum, Thunia, Brachycarythis, Satyrium, Corybas, Geodorum, Zeuxine,  Tropidia,

have the Hengduan Mountain Region as the northern limit of distribution.   Of 151 species

with 4 varieties, 41 species with 4 varieties are endemic to China, and 14 species with 3 varie-

ties of them are endemic to the area, making up 3.86% of the total in the region under

discussion.

      There are 41 genera (containing 189 species with 5 varieties) of the temperate distribution,

which occur in the region.  Among them Platanthera (22 species with 1 variety), Cypripe-

dium (17 species), Herminium (16 species), Amitostigma (15 species with 1 variety), Orchis

(12 species), Hemipilia (8 species with 1 variety), Neottianthe (4 species), Gymnadenia (4

species), Diphylax (3 species), Bletilla (3 species), have the Hengduan Mountain Region as the

distribution centre and differentiation centre. Among the 189 species with 5 varieties, 111 species

with 5 varieties are endemic to China, and 54 species with 5 varieties are endemic to the area,

making up 14.88% of the total of orchids in the Hengduan Mountain Region. Although the

number of temperate distribution genera is smaller than that of tropical distribution ones, se-

veral points may be mentioned:

      (1)  The Hengduan Mountain Region is distribution centre and differentiation centre of

a number of temperate genera in China, and is the northern limit of many genera mainly dis-

tributed in the tropics.

      (2)  The number in the former category is obviously larger than that in the latter.

      (3)  Endemic species in the former category in the area are over three times as many as

those in the latter.

      The differentiation of species of the temperate distribution genera is obviously stronger

than the tropical ones, which characterizes the orchid flora in the area as the temperate one.

      The life forms of genera.  The orchid flora in the Hengduan Mountain Region so far

known comprises 91 genera, among which 51 are terrestrial, 32 epiphytic and 8 saprophytic,

thus with the terrestrial one dominant.

      The analysis of  species:    The orchid flora in the Hengduan Mountain Region

 so far known comprises 363 species with 9 varieties.  Their distribution patterns and floristic

 components, to which they belong, are indicated as follows:

       (1)  Fifty four species, belonging to 33 genera, are widespread, covering the whole East-

 Asian Region, but 6 of them are endemic to China.

       (2)  Forty four species, belonging to 27 genera, are the elements of the Sino-Japanese

 Subregion, but 22 species of them are endemic to China.

   (3)  One hundred and ninety five species with nine varieties, belonging to 53 genera,

are the elements of the Sino-Himalayan Subregion under discussion:

      (A)  Four species (i.e. Aphyllorchis alpine, Listera divaricata, L. pinetorum and Oreor-

chis micrantha) are distributed in the Himalayan Region and S. E. Xizang (Tibet), western

part of this region.

      (B)  Twenty five species, belonging to 17 genera, are distributed in N. W. Yunnan and

the Himalayan Region (Appendix, 1.).

      (C)  Sixteen species, belonging to 11 genera, are distributed in the Himalayan region

and W. Sichuan.  Among them 6 species occur only with Mt.  Emei as the easternmost limit

 and 10 species occur in the region west of Mt. Emei.

      (D)  Ten species, belonging to 9 genera, are distributed in the Himalayan region, this

region and S. Shaanxi, S. Gansu or S. E. Qinghai.

      (E)  Eight species, belonging to 6 genera, are distributed in the Himalayan region and

this region.  Among them 6 species have their range extending eastwards to Guizhou and 2

species eastwards to Guangxi.

      (F)  Five species, belonging to 5 genera, having their range extending from this region

southwards to N. Burma.

      (G)  One handred and twenty seven species with nine varieties are endemic to China

behind discussion.

      (4) (A)  Three species (i.e. Anoectochilus moulmeinensis, Bulbophyllum forrestii and

Liparis chapaensis) are distributed in Indo-China, Burma and the region.

      (B)  Nine species, belonging to 7 genera, are distributed in Indo-China, N. E. India

and this region.

      (C)  Forty six species, belonging to 21 genera, are distributed in Indo-China, the Hima-

layan Region and this region (Appendix, 2.).

      (D)  Twelve species, belonging to 11 genera, are distributed in Indo-China and this re-

gion (Appendix, 3.)

      3.  The vicarism is obvious in the orchid flora of the Hengduan Mountain Region.

      There are 10 species-pairs (in genera Calanthe, Tropidia, Anoectochilus, Mischobulbum,

Bulbophyllum, Gymnadenia, Pogonia, Tipularia, Tulotis, Orchis, etc.) of the horizontal vica-

rism and 7 species-pairs (in genera Epigeneium, Epipogium, Platanthera, Pogonia, etc.) of the

vertical vicarism in the region.

      4.  The endemic species are prolific in the region.

      In the orchid flora of the Hengduan Mountain Region there are 155 species and 9 varie-

ties endemic to China:

      (1)  Six species are widespread in the whole East-Asian Region.

      (2)  Twenty two species are the elements of the Sino-Japanese Subregion.

      (3)  One hundred and twenty seven species with nine varieties are the elements of the

Sino-Himalayan Subregion.  Among them 69 species with 5 varieties are endemic to the re-

gion (Appendix, 4.), making up 19% of the total in the region; other 58 species with 4 varie-

ties are distributed in the region and neighbouring regions or provinces of it (Appendix, 5.).

      5.  Remarkable differentiation of the orchid flora in the Hengduan Mountain Region is

shown by evident vicarism and abundance of endemic elements, exampled by  Amitostigma,

Herminium, Orchis, Cypripedium, Platanthera, etc. and one group of Platanthera, which is

confined to the south fringe of the Xizang (Tibet) Plateau-Hengduan Mountain Region.  The

group consists of 12 species, of which one (P.  edgeworthii) is distributed in the Western Hi-

malayas from Hazara in Pakistan to Kumaun in India, and all the other 11 species (i.e.P.

stenantha, P. bakeriana, P. roseotincta, P. deflexilabella, P. longiglandula, P. exilliana, P.

chiloglossa, P. leptocaulon, P. platantheroides, P. clavigera and P. latilabris) occur in China,

with 3 of them (i.e.P. deflexilabella, P. longiglandula and P. chiloglossa) endemic to China.

According to their structure of gynostemum and form of labellum they belong to Platanthera

without question, although they are different from the other members of Platanthera in stigma

convex (not concave) and sepals mammillary-ciliate, stigma exhibits a series of evolutionary

trends in part of species, from stigma single, convex, elliptic and located near rear of spur

mouth (in P. stenantha) to stigma single, suddle, and located near front of spur mouth (in P.

bakeriana) and to stigma double, separate and located at front of spur mouth in the other

ten species.

      The group in Platanthera is only confined to the area from the south fringe of the Xizang

(Tibet) Plateau to the Hengduan Mountain Region.  It seems that the genus has been affected

by intense lift of the area, causing variation and differentiation and giving rise to the group

due to the long-term natural selection.  Mt. Emei in Sichuan Province is the eastern limit of

distribution of the group, where there are three spcies, among which two (P. deflexilabella

and P. longiglandula) are endemic to the mountains.

      In addition, among Risleya (1 species), Diphylax (3 species) and Diplomeris (2 species),

three genera typical of distribution in the Sino-Himalayan Subregion, Risleya and   Diphylax

have Mt.  Emei as their eastern limit.  Eleven species, belonging  to elements of the  Sino-

Japanese Subregion, occur only from Japan to Western Sichuan with Mt. Emei as the western

limit.  Among nine species, belonging to elements of the Sino-Himalayan Subregion, six occur

from the Himalayas to W. Sichuan and three of them are endemic to the Hengduan Mountain

Region, with Mt. Emei as their eastern limit of distribution.  There are eight endemic spe-

cies and one variety of orchids in Mt. Emei, making up about 11.59% of the total endemic

species in the Hengduan Mountain Region.  Orchid floristic elements in Mt. Emei are obvi-

ously different from those in Mt. Jinfo, the former being mainly of the Sino-Himalayan Su-

bregion, while the latter being mainly of the Sino-Japanese Subregion.  From the distribu-

tion patterns of the orchid floristic elements in the Hengduan Mountain Region and Eastern

China, the Emei Mountain is considered important for drawing a boundary line between the

Sino-Japanese Subregion and the Sino-Himalayan Subregion.

      The discussion may be summarized as follows: the floristic features of the orchid flora in

the Hengduan Mountain Region are: (1) rich in species, complex in geographical components,

eminent vicarism and differentiation, and prolific in endemic species; (2) terrestrial life form

 is dominant one; (3) mainly consisting of temperate and subtropical East-Asian elements, es-

 pecially, elements of Sino-Himalayan Subregion, though with some tropical elements and elem-

ents of other regions.

Key words: Hengduan Mountain Region, orchids, floristic composition and features