1. Uplifting of Qinghai-Xizang plateau has brought great influence on the origina-
tion and distribution of species inside the genus Salix. There are 91 sp. (incl. 2 cult.
sp.), 16 var. and 3 f. belonging to 15 Sect. in this region, among these species the en-
demics attain to 58 sp., 14 var. and 3 f. So it has become one of the most important
centres of distribution of Salix in the world. Species common with other regions attain
only to 32. Thus it is also clear that correlation between salicaceous flora in this re-
gion and that of other regions is not so much developed, and that the salicaceous flora
of Qinghai-Xizang plateau was mainly originated autochthonously during the upheaval
of plateau.
2. Along a demarcation line delineated from Gyirong through Lhasa and Qamdo to
Lanzhou, to the north-western region the total number of species of this genus is sum-
med up to 7 sp. and 1 var. (incl. 2 cult. sp.), and they distribute only in the West Hima-
laya and Pamir-Kunlun regions. Besides 2 cult. sp., there is only 1 endemic, and
others all should be migrants from Europe or West Asia. In the south-eastern part, be-
cause the climate is moister, the species of Salix may be summed up to 84 sp., 15 var.
and 3 f., among them 73 sp., 20 var. and 3 f. are endemics, accounting for 68 percent
of the total.
3. In East Himalaya and South Henduan Shan (southward of lat. 30°N.) there
are 78 sp., 12 var. and 4 f., among them 50 sp., 10 var. and 2 f. are endemics. They
represent the different stages of phylogenetic development of this genus. So here may
be the centre of origination and distribution of Salix species in the all Sino-Himalaya
flora. The common species between East Himalaya and South Henduan Shan regions
attain to 41. Because the latter forms a part of Sichuan and Yunnan plateau and the
former did not become a land until Quaternary Period, the plants of the former mainly
are the migrants from the latter.
4. The most characteristic group of Salix in this region is Sect. Lindleyanae
Schneid. with a total of 18 sp. and 1 var. This group adapting to the somewhat en-
vironment changes is quite different from Sect. Retusae A. Kern. in the Arctic and high
mountains of higher latitudes in many characters, so it should be originated autochto-
nously, and it is certainly not a migrant from Arctic. This Sect. seems to be developed
from Sect. Floccosae Hao and in turn from Sect. Sclerophyllae Schneid. and Sect. Den-
ticulatae Schneid. This developmental direction has assumed an important branch in the
phylogenetic development of the whole genus.
5. In addition, there are two interesting and important regions on the north-eastern
and eastern to Qinghai-Xizang Plateau, i. e. on the north-east Anymaqen Shan (Amne-
machin mountain) and on the east Qiong Lai Shan. There are many endemic species
pertaining to these two parts, among these species some may be ancient relicts since
Tertiary. It is to be expected that more additional scientific results will be obtained
after some more extensive works done in these two regions.
