OF SIKKIM-HIMALAYA. 11 
The Neclgherries, Ceylon, and the Malay Archipelago contain, each, some species which prove the affinity of their 
Floras to that of the Himalaya. The same is the case“with the great mountains of Northern Asia, Central, Southern, and, 
especially, Eastern Hurope, the Ural, and Pontus. ‘The genus extends even to the Polar regions, diminishing in the size 
of the species and number as we recede from the Himalaya: in North America they appear again, though under a very 
different aspect from that they present on the subtropical mountains of Asia. ’ 
Wide though this distinction is, it is far from uniform, the Himalaya itself offering most remarkable anomalies. My 
friend Dr. Thomson (now engaged in a botanical mission to Thibet) informs me that the genus is not found in 
Cashmere ; nor, during all the wanderings of that intrepid and indefatigable naturalist in the Trans-Sutledge Himalaya 
and Thibet, has he met with one representative of it. He detected, indeed, in the country south of the Chenaub, both the 
A. arboreum and R. campanulatum, and which is probably their western limit. 
In North-west India, the genus Rhododendron is first seen on the Kunawur hills, and advancing east, follows 
the sub-Himalayan range for its whole length, the- species increasing in number as far as Sikkim and Bootan; thence 
the genus is continued to the Mishmee hills, the eastern extremity of the range, crossing the Brahmaputra to that 
lofty range which divides the water-shed of the Irawaddi from that of the Brahmaputra. 
Though scarcely found, throughout this long line of upwards of 1,200 miles, below 4,000 feet, the Rhododendrons 
still affect a warm and damp climate, where the winters are mild. The English naturalist, who is only familiar 
with the comparatively small hardy American and European species, would scarcely expect this. A certain degree of 
winter-cold and perpetual humidity is necessary; but the summer-heat is quite tropical where some of the genus 
prevail, and snow rarely falls and never rests on several of those peculiar to Sikkim. 
ZR. arboreum, according to Captain Madden, inhabits various localities between 3,000 and 10,000 feet: this is in 
Kamaoon, where, of course, the genus would descend lowest ; and the range is incomparably greater than that of any other 
species, at least of those found. in Sikkim.* Dr. Griffith, after extended wanderings in Bootan, gives the limits of the genus 
in that country as between 4,292 and 12,478 feet, which is a lower level by 3,000 feet than they are known to descend to 
in Sikkim. In the extreme east of Assam, where the Himalaya itself diverges or sends lofty spurs to stem the 
Brahmaputra, on the Phien Pass to Ava, Rhododendrons ascend from 5,400 to 12,000 fect, to the upper limit of 
arboreous vegetation, and perhaps still higher. 
During my limited excursions in Sikkim, I parked eleven species (and I believe that more exist), a greater 
number than Griffith obtained in Bootan; so that I cannot but regard this longitude as the head-quarters of the 
genus in the Himalaya, and that chain as the especial region of the genus in the Old World. Here too I may 
remark (as is the case with the Conifere of Tasmania and Cactee of Mexico), the species are most limited in habitat, 
where, numerically, the genus is the largest, the 2. arboreum, however, having a much wider range than any other 
species found in Sikkim. 
* Dr. Hooker had here inserted “where 2. arboreum is unknown,” that is, in Sikkim. But one of his own excellent figures, sent home 
as representing a new species, is, I have no hesitation in saying, the true 2. arboreum, coinciding entirely with the original figure of Sir James 
E. Smith (Exotic Botany, Tab. 6), and with original specimens given me by the same distinguished botanist and existing in my own Herbarium. 
Nor need we be surprised that Dr. Hooker should have fallen into this error, with few books and no authentic specimens to consult ; 
especially when it is borne in mind that his eye had been accustomed to the plants that pass under that name in our gardens, but which 
have been so hybridized by cultivators, either to increase their beauty or with the intention of rendering the offspring more hardy, that an 
original plant or tree of Rhododendron arborewm is almost as rare in England as is the normal single-flowered state of the Corchorus 
(Kerria) Japonica. Let it be further observed that other distinguished Botanists have confounded distinct species with the 2. arboreum: 1 
allude especially to the plant so called by Dr. Wight of the Neelgherries (cones Plant. Ind. Orient. tab. 1201), which is the 2. Nilagiricum 
of Zenker (Plant. Nilag. cum Ic., and of Bot. Mag. tab. 4381). No one who compares native specimens of these two plants can have 
any hesitation in pronouncing them distinct. Ep. 
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