NORTH-WEST MONGOLIA AND CHINESE DZUNOAEIA. 387 



Separating the Yenisei basin from the plateau of North-West Mongolia 

 lie the Tannu-ola mountains, in latitude 60-61°. 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 Up{)er Yenisei plateau to the northern 

 slopes of the Tannu-ola mountains. Ascending the Ami! River, a tributary 

 which flows into the Yenisei near Minnusinsk, the party, consisting of a 

 caravan of 24 horees, reached the watershed between that river and the tribu- 

 taries of the Upper Bei Kern 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 Eiver 

 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 Kemchik, where a fresh 

 caravan 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-arctic 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 Larch-forest association. South of this zone 

 we reached that of the sub-arctic forest. The dominant species were Abies 

 sibirica, Picea obovata, and Pinus sibiyica *. The sub-arctic 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. 



