4 
NORTH-WEST MONGOLIA AND CHINESE DZUNGARIA, 387 
Separating the Yenisei basin from the plateau of North-West Mongolia 
lie the Tannu-ola mountains, in latitude 60-617. They form the second 
step of the plateau, and after crossing them the traveller finds himself on 
the floor of the Mongolian desert plateau, which from this point southwards 
averages about 5000 feet in altitude. 
The first section of the journey was undertaken from the Siberian lowlands 
across the Sayansk mountains and the Upper Yenisei plateau to the northern 
slopes of the Tannu-ola mountains. Ascending the Amil River, a tributary 
which flows into the Yenisei near Minnusinsk, the party, consisting of a 
caravan of 24 horses, reached the watershed between that river and the tribu- 
taries of the Upper Bei Kem in June 1910. After plunging through dense 
forests of Siberian pine and spruce, we crossed the Sayansk mountains by a 
low pass and reached the Upper Yenisei plateau. Descending the Sisti Kem 
tributary, we explored several of the valleys which drain the right bank of the 
Bei Kem. Several side expeditions were undertaken in boats, which in this 
district are made by the Siberian fur-traders out of dug-out poplar logs, and 
eventually the whole party made a raft and floated down the Bei Kem River 
for 150 miles, shooting a series of rapids about 50 miles above the junction 
of the Bei Kem and Khua Kem. The party at last arrived at Dja Kul, a 
small frontier trading centre on the steppes of the Kemehik, where a fresh 
aravan was made up for the journey across the North-West Mongolian 
plateau. 
The observations on the floral and botanical conditions on this first part of 
the journey can be divided into two sections, one dealing with the northern 
slopes of the Sayansk mountains, and the other with the valley of the Bei 
Kem in the Upper Yenisei plateau. 
Taking the first section, I can tabulate the following observations while 
ascending the Amil River. 
After leaving the steppes south of the Minnusinsk district, a thin zone of 
Pinus sylvestris forest appears and forms an. intermediate zone between the 
steppes and the dense sub-arctie forests further to the south. Pinus sylvestris 
attains its best development here, and the ground flora is accompanied by 
many species of the steppes to the north as well as several species of herbs, 
which I describe later in the Lareh-forest association. South of this zone 
we reached that of the sub-aretie forest. The dorninant species were Abies 
sibirica, Picea obovata, and Pinus sibirica *. The sub-aretie forest zone lay 
scattered along the northern side of the different uplifts, which compose the 
Sayansk system, and varied from 70 to 100 miles in width from north to 
south. Immense areas of swamp punctuated the dense jungle of Siberian 
* The specimens collected on the expedition are Pinus Cembra, Linn, var. sibirica, 
P.Mayr. The variety seems only to differ physiologically from the species.—N. D. SIMPSON. 
