REVIEW—THE RHODODENDRONS OF SIKKIM-HIMALAYA. 157 
which I gazed! The heaven-ward outline was projected against a pale 
blue sky, while little detached patches of mist clung here and there to 
the highest peaks, and were tinged golden-yellow or rosy-red by the 
rising sun, which touched those elevated points long before it reached 
the lower position which I occupied. 
“ «Such is the aspect of the Himalayan range at early morning. As 
the sun’s rays dart into the many valleys which lie between the snowy 
mountains and Darjeeling, the stagnant air contained in the low re- 
cesses becomes quickly heated ; heavy masses of vapour, dense, white, 
and keenly defined, arise from the hollows, meet over the crests of the 
hills, cling to the forests on their summits, enlarge, unite and ascend 
rapidly to the rarefied regions above; a phenomenon so suddenly 
developed, that the consequent withdrawal from the spectator’s gaze of 
the stupendous scenery beyond looks like the work of magic.’ Such 
is the region of the Indian Rhododendrons. 
« The maximum of Rhododendrons appears to be in Asia, and their 
head-quarters are on the lofty ranges of the eastern Himalaya, where 
the mild and moist atmosphere is eminently suited to their habit. 
‘“* A certain degree of winter cold and perpetual humidity is neces- 
sary, but the summer heat is quite tropical where some of the genus 
prevail, and snow rarely falls, and never rests on several of those pecu- 
liar to Sikkim.” In the case of R. Falconeri, which grows on the 
summit of Tonglo, at an elevation of 10,000 feet, Dr. Hooker remarks, 
that the temperature of the earth in which it grew was, in the middle 
_ of May, at 27 inches below the surface, where the roots are chiefly 
developed, 49° 5’ at all hours of the day; that of the air varied from 
50° to 60°. 
These observations, and the mean temperatures previously quoted, 
show, as is well remarked in the Gardeners’ Journal, that spring and 
not mid-winter is the season of trial, not only in the case of the Indian 
Rhododendrons, but in that of very many other half-hardy plants from 
various parts of the world, especially from the mountain regions of 
India and South America. Comparing the figures just referred to, it 
will be seen that during the months of November, December, and 
January, the difference in the mean temperatures of London and 
Darjeeling is about 4° only, and the same difference is indicated for 
the months of July, August, and September. On the other hand, 
February and May, the transition months between winter and spring, 
and spring and summer, show a difference of 6° ; the spring months of 
March and April, a difference of 11° and 10° respectively ; and in 
autumn, too, as shown in October, the difference is 9°. ‘ Here,” as 
the journal above referred to observes, ‘* we have a solution of the 
cause of our want of success in cultivating tender plants in the variable 
climate of Great Britain: our springs are late, and cold, and change- 
able; and while the winters and summers of Darjeeling and London 
differ but 3° or 4’, the springs and autumns show a difference of 10° 
and 12°. This accounts for the excitable nature and early growth of 
many of our half-hardy Indian plants, as well as the tendency of many 
such to grow to a late period of the autumn.” 
But though we cannot hope to grow these fine things, except in 
some of the most favoured parts of England and Ireland, yet the dis- 
covery, and the probable speedy introduction of them, are matters of 
great horticultural interest. ‘“ It is true that plants originally tender 
