On the principle of unity of the phylogeny and the geographical distribution in plants,

the distribution centre, time and place of origin and formation of the modern distribution pattern of

the genus Kengyilia are discussed in the present paper. Kengyilia is a small genus including 3 sec-

tious, 26 species and 6 varieties in Poaceae. The genus is distributed in China, Kazakhstan, Kir-

ghizia, Tadzhikistan, Afghanistan and Iran. It adapts to the temperate habitats, and also exists in

the environments of high elevation. According to Takhtajan‘ s (1978) regionalization of the world

flora, Kengyilia is distributed in the Eastern Asiatic Region and the Irano-Turanian Region of the

Holarctic Kingdom. Six species occur in the Eastern Asiatic Region where endemic species are ab-

sent. In the Irano-Turanian Region there exist 26 species and 6 varieties, 26 of which are endemic

taxa, and in this region the highest concentration of the taxa occurs in Tibet Province, with 19 spe-

cies and 6 varieties. In China, according to Wu‘ s(1979) regionalization of the Chinese flora,

Kengyilia is found in 4 regions. Among them the Qinghai-Xizang Plateau subkingdom is the most

abundant for species and varieties. The area totally has 16 species and 6 varieties, taking up 68%

of the total taxa of Kengyilia and 75% of all taxa of Chinese Kengyilia, and these taxa include the

primitive to the most advanced ones in the genus. These facts indicate that the Qinghai-Xizang Pla-

teau is the distribution center of Kengyilia. The primitive section in Kengyilia is sect. Kengyilia,

consisting of 9 species. It is highly centred in the Tianshan area where 5 species occur, of which

K. zhaosuensis is the most primitive species in the genus. The relatively primitive section of the ge-

nus is sect. Stenachyra L. B. Cai which contains 10 species and 3 varieties. Two of its species also

grow in Tianshan area. In Tianshan area, on the contrary, there is not the sect. Hyalolepis (Nevs-

ki) L. B. Cai which is considered as the most advanced section in the genus. Based on our study

and relevant references, the closely related group of Kengyilia is the genus Roegneria C. Koch.

Some species of Roegneria is not only distributed in Tianshan area, but also their habitats in the ar-

ea agree with that of primitive species of Kengyilia. Moreover, since Tianshan Mountains were

raised once more in the Neogene, the area had possessed the natural conditions to produce and mul-

tiply Kengyilia plants. Hence, this area is likely to be the origin place of Kengyilia. Before the

Mesozoic, the ocean and land in Tianshan area changed greatly. Being a xerophytic genus, Kengy-

ilia could not live in the environment of waters. From the Mesozoic to the end of the early Tertiary of Cenozoic, the crustal movement in Tianshan area was tending toward tranquility. Owing to the denu-

dation, the original high mountains were leveled forming the primary plain. The landforms and en-

vironment in Tianshan area resembled those of its adjacent areas. Consequently, it was still unlikely

to cause the birth of Kengyilia. Only in the Neogene of Cenozoic and even in the early period of the

Quaternary, the primary plain in Tianshan area began to rise rapidly. The tremendous changes of

landfonns and environment had taken place in the area. In the course of adapting to this change,

the ancestor of Kengyilia produced probably the plant of the genus during this time. Besides, before

the end of the early Tertiary, the climate in Tiaushan area belonged to the subtropic type. The damp

and hot climate was unfavourable to the birth of Kengyila which possesses the temperate characteris-

tics; while only from the end of the early Tertiary, up to the end of the Neogene, the climate in the

area was gradually getting into aridity and coolness, suitable for the existence and multiplication of

Kengyilia plants. In addition, the origin time of Kengyilia fits in with the origin of its closely relat-

od genus and the fossil record of Poaceae. After Kengyilia originated from the Tianshan ama, be-

sides development and differentiation, it dispersed toward all directions. Nevertheless, owing to the

limitations of the environment in these regions neighbouring to the Tlanshan area, especially the sep-

arations of the Tatimu Basin and the Zhungaer Basin, the dispersal of the genus seems to be in three

main mutes: the first route is along the western Tianshan Mountains, toward the southwest through

the Pamirs; the second is along the eastern Tianshan Mountains, toward the southeast via the Qilian

Mountains; the third is northward across the Alatao Mountains, along the Baerluke Mountains and

toward the north by east via the Wurikexiayi Mountains. Among the three mutes, the southwestward

route is the mainest, while the northward the weakest. Kengyilia plant entered the Qinghai-Xizang

Plateau from two sides of east and west by the southwestward and the southeastwant mutes. In the

Qinghai-Xizang Plateau, it fully developed and differentiated, producing the most advanced sect.