EAST NEPAL AND THE SIKKIM HIMALAYA MOUNTAINS. 115 



in other parts of the world, and some even of the hot plains of 

 Bengal, ascend to 12,000 and even 15,000 feet on the Himalaya, 

 unaffected by diminished pressure. Any quantity of species 

 from low countries may be cultivated, and some have been for 

 a<?es, at 10,000 to 14,000 feet, without change. It is the same 

 with man and the lower animals ; innumerable instances may 

 with ease be adduced of pressure alone inducing no appreciable 

 change, whilst there is an absence of any proof to the contrary. 

 The phenomena that accompany diminished pressure are the real 

 ob^acles to the cultivation of alpine plants, of which cold and 

 the excessive climate are perhaps the most formidable. Plants 

 that grow in localities marked by sudden extremes of heat and 

 cold are always very variable in stature, habit, and foliage. 

 In a state of nature we say the plants " accommodate them- 

 selves" to these changes, and so they do within certain limits; 

 but for one that survives of all the seeds that germinate in these 

 inhospitable localities, thousands die. In our gardens we can 

 jieither imitate the conditions of an alpine climate, nor otfer 

 others suited to the plants of such climates. 



Light. — The plants of the different zones are very differently 

 situated with regard to this element. The forest region, which 

 so uniformly extends to 12,000 feet, shuts out much light from 

 the plants that grow in it, and such are generally pale-coloured 

 or white, — as, amongst rliododendrons, R. Hodgsoni, R. camel- 

 lia-jiorum^ R. argenteum, R. Falconeri, &c. &c. On the other 

 hand, many of the most gorgeously coloured ones abound in the 

 sunniest and lightest spots, as R. fidgeiis, R. arboreutn, R. 

 TliomsofU. Still it must be recollected that many species emi- 

 nently abundant in the sunniest exposures are pale flowered, as 

 R. Wightii.^.ccunpylocarpum, R. lilacitium, and Jl. Griffithii ; 

 and that some gorgeous species are very frequent in deep woods, 

 as R. arbo7-eum itself, R. Tltowsoni, R. baibatum, R. cmnaba- 

 linum, and that their colour is not materially lessened, except 

 the shade be unnaturally deep. It is hence difficult to appre- 

 ciate the direct influence of sunlight on the individual plants in 

 the Himalaya. If on the other hand we compare all the species 

 as there existing, with their congeners in higher latitudes, it 

 becomes evident that the balance in favour of gorgeous colouring 

 is greatly on the side of the Himalaya ; which renders it probable 

 that the more direct sun's beam of lat. 26° to 28° has an in- 

 fluence which its slanting rays in high latitudes have not. This 

 is a very interesting subject for future investigation ; it cannot 

 be satisfactorily dealt with, except by accurately estimating the 

 number of coloured species in two well-marked localities. One 

 remarkable fact has already come prominently before me, which is, 

 that tlie R. ciliatnm. now flowering abundantly at Kew, has larger 



