72 CLIMATE AND VEGETATION OV 



liaving the leaves of R. campanulatum, and capitula and flowers 

 of a scarlet variety of R. arboreum ; but considering how variable 

 R. campanulutum is in colour, and that it assumes a denser capi- 

 tuhnn in its variety ceruginosurn (which I published as a species), 

 I sliould be more inclined to rank. R. fulgens as a permanent 

 variety of that species tlian as a mule between it and a plant with 

 a totally dissimilar leaf, which is comparatively tender, and which 

 grows 4000 feet lower down. The principle of hybridization is a 

 dangerous one to admit heedlessly in these cases, and should only 

 be resorted to as a forlorn hope, when every other attempt to 

 account for the Protean habits of an assemblage of species has 

 failed : such I cannot consider to be the case with the Sikkim 

 Rhododendrons ; and though I do not abandon the idea in theory, 

 I shall not adopt it in this emergency. 



Epiphytical Habits of some Species. — Much undue import- 

 ance has been given to the fact of some kinds growing habitu- 

 ally epiphytically (R. Dalhousice, R. camelliccjiorum^ R. pendu- 

 lum^, and it has been supposed that much difficulty must attend 

 their cultivation. Having occasionally seen all these species 

 growing on rocks, and the two latter sometimes becoming erect, 

 and that always in exposed but very moist localities, I have 

 been induced to attribute their predilection for tlie branches 

 of trees to their weak habit and want of light elsewhere. Being 

 plants of the forest region, and unable to contend against the 

 vigorous undergrowth that prevails there, the offspring of sucli 

 seeds as fall on the ground are choked, whilst the perennially 

 humid atmosphere supports such as sprout on the mossy limbs of 

 trees, where they receive the stimulus of light. R. Dalhousice, 

 for instance, which is never found on the ground in the woods of 

 Darjiling, grows in thousands on the clay and mould banks of the 

 roads which are cut through the forest, the young plants coming 

 up in profusion as soon as the cuttings are made : these, however, 

 seldom attain any size, from the too great exposure of the soil, 

 which in the dry season rapidly parches during a short day's heat. 

 In Dr. Campbell's garden at Darjiling there is a perpendicular 

 bank, 15 feet high, exposed to the west, and partly sheltered 

 from the south-west by a house. R. Dalhousice has annually 

 appeared on this, the seeds being imported by winds or birds 

 from the neighbouring forest. The seedlings, however, perished 

 till within the last two years, since which time abundance of Lyco- 

 jwdiuin clavatum and a Selaginella, with Marclinntia, retain so 

 constant a supply of moisture that the plants now flourish and 

 flower in perfection. Though not equal to the herbaceous, the 

 number of small shrubby forest plants that grow on the trees in 

 these damp regions is very great, especially the orchideous. 

 Those that do so most habitually are species of Vaccinium 



