154 
TEE vegetation OF THE ZEMU 
In this upper region three distinct divisions may be noted : 
I. The slopes from Nachegoh to the Thangchung La are open, 
free from snow at an early date, with tiny rivulets which soon 
become dry in the summer. The north side of the valley is remark- 
able for the persistence, up to nearly 17,000 feet, of species usually 
considered as belonging to lower altitudes. The typical 13,000 
feet flora sends up representatives to nearly the top of the ridge 
and the plants characteristic of extreme alpine Sikkim are slow 
cO appear. 
II. The southern slopes, lying under the brow of the mighty 
range are sheltered from the sun and retain here and there the 
snow even in July down to 14 — 15,000 feet. Rhododendrons here 
tend to assert themselves to the exclusion of other genera and the 
slopes lack the variety of the north side, though alpines are 
more prevalent and appear at a much lower altitude. 
III. The bleak area at the top of the valley where owing to 
the proximity of the glacier, the limit of vegetation appears to be 
reached sooner. The flora of this area approaches that of the 
second but is scantier. 
Taken as a whole the valley is undoubtedly a transition from 
the moist prolific area such as prevails to the south and is typified 
by Jongri, to the dry area of Tibetan Sikkim lying beyond the 
The La. Though much poorer in species than the Jongri area it 
has on the whole more afiinities with it than with the Llonakh. 
The lack of epiphytic forms, the comparatively scarcity of ferns, 
mosses, lichens, show an approximation, however, to what we 
found in the dry areas of Llonakh. 
The Zemu valley forms undoubtedly the dividing line between 
these two types of vegetation ; its flora is that of an attenuated 
Jongri while the Llonakh flora though less rich in species has a 
‘ facies ’’ of its own. 
The valley is a very short one and gives no opportunity for a 
particularly varied flora. The above generalisations are, we think, 
as complete as the subject demands. 
After one day at Lachen and one to reach the junction of the 
Zemu and Llonakh, we commenced the ascent of the latter. There 
were sheep-tracks for the first mile and then undisturbed rhododen- 
dron jungle. We kept at first to the right bank; the left is closed 
at 11,000 feet by a huge precipice. With much lalTOur we reached 
12,700 feet where the right bank becomes locked in by precipices. 
We collected materials for a bridge and camped among the 
