Abstract:

 1)  The Compositae in Tibet so far known comprise 508 species and 88 genera,

which nearly amounts to one fourth of the total number of genera and one third of the

total number of species of Compositae in all China, if the number of 2290 species and 220

genera have respectively been counted in all China. In Tibet there are all tribes of Com-

positae known in China, and surprisingly, the large tribes in Tibetan Compositae are

also large ones in all China and the small tribes in Tibet are also small ones in all China.

Generally speaking, the large genera in Tibet are also large ones in all China and the

small genera in Tibet are likewise small ones in all China. In this sense it is reasonable to

say that the Compositae flora of Tibet is an epitome of the Compositae flora of all China.

     In the Compositae flora of Tibet, there are only 5 large genera each containing 30

species or more. They are Aster, Artemisia, Senecio, Saussurea and Cremanthodium. And

5 genera each containing 10—29 species. They are Erigeron, Anaphalis, Leontopodium,

Ajania, Ligularia and Taraxacum. In addition, there are 77 small genera, namely 87%

of the total of Compositae genera in Tibet, each comprising 1—9 species, such as Aja-niopsis, Cavea and Vernonia, etc.

     2)  The constituents of Compositae flora in Tibet is very closely related to those of

Sichuan-Yunnan provinces with 59 genera and 250 species in common. Such a situation

is evidently brought about by the geographycal proximity in which the Hengtuang Shan

Range links southeastern and eastern Tibet with northern and northwestern Sichuan-

Ynnnan.  With India the Tibetan Compositae have 59 genera and 132 species in common,

also showing close floristic relationships between the two regions. Apparently the floris-

tic exchange of Compositae between Tibet and India is realized by way of the mountain

range of the Himalayas.  The mountain range of the Himalayas, including the parallel

ranges, plays a important role as a bridge hereby some members of the Compositae of

western or northern Central Asia and of the northern Africa or of western Asia have

migrated eastwards or southeastwards as far as the southern part of Fibet and northern

part of India, or hereby some Compositae plants of eastern and southeastern Asia or

Asia Media have migrated northwestwards as the northern part of Central Asia.

     Some of the species and genera in common to both Tibet and Sinjiang indicate that

this weak floristical relationship between these regions is principally realized through two

migration routes: one migration route is by way of the Himalayas including the parallel

ranges to Pamir Plataeu and Tien Shan, or vice versa. The other migration route is by

way of northern Sinjiang to Mongolia, eastern Inner Mongolia, southwards to Gansu,

Qinghai (or western Sichuan), eastern Tibet up to the Himalayas, or vice versa.

     However, Tibet is not entirely situated at a migration crossroad of the floral ele-

ments. An ample amount of the data shows that Compositae flora have a particular

capability of development in Tibet. of the total number of species of Tibetan Com-

positae, 102 species and 1 genus (Ajaniopsis Shih) are endemic. Besides, 8 genera are re-

gional endemics with their range extending to its neighbourhood. The higher percentage

of endemics at specific level than at generic in Tibetan Compositae may be a result of

active speciation in response to the new enviromental conditions created by the uplifting

of the Himalayas.  The flora in Tibetan Plateau as a whole appears to be of a younger

age.

      3) The uprising of the Himalayas and of the Tibetan Plateau accompanied by the

ultraviolet ray radiation, the microthermal climate and the high wind pressure has, no

doubt, played a profound influence upon the speciation of the native elements of Tibetan

Compositae. The recent speciation is the main trend in the development of the Com-

positae flora native in Tibet in the wake of upheaval of the plateau.