Not so common but larger and handsomer than the dendrobiums are the cymbidiums, of which there are sixteen different species, usually with long grassy leaves and many-flowered drooping racemes with large handsome flowers. A very sweet-scented species is the Cymbidium eburneum, which is common between elevations of 1,000 to 3,000 feet, and flowers during March and April. The prevailing colour of the flowers is an ivory white, but the ridge on the lip is a brilliant yellow. This also may be seen at Kew in March.
These are some of the commonest orchids and all now grow in England, so that we can begin to get a footing in the forest and not feel that it is so completely strange to us. And as we ascend higher we shall find many more friends among the flowers. And to guide us among the trees and flowers we fortunately have Sir Joseph Hooker, who in his "Himalayan Journals" has described this botanist's paradise in loving detail, so we cannot do better than follow him. Amid the many plants he mentions we can only select a few, but these few will at least help to give us some conception of the whole and show the range of variation as we ascend.
As we proceed higher up the valley to an altitude of about 4,000 feet, European trees and plants begin to be intermingled with the tropical vegetation. Hornbeams appear, and birch, willow, alder, and walnut grow side by side with wild plantains, palms, and gigantic bamboos. Brambles, speedwells, forget-me-nots, and nettles grow mixed with figs, balsams, peppers, and huge climbing vines. The wild English strawberry is found on the ground, while above tropical orchids like the dendrobiums cover the trunks of the oaks. The bracken and the club-moss of our British moors grow associated with tree-ferns. And English grow alongside Himalayan mosses.
The valley itself continues of the same character—deep with its steep sides clothed in forest and the path scrambling over spurs, making wide detours up side valleys, or scraping along the sides of cliffs which stand perpendicularly over the raging river below. Only here and there are clearings in the forest where Lepchas or Nepalese have built themselves a few wooden houses and roughly cultivated the land. Otherwise we are under the same green mantle of forest which extends everywhere over the mountains; and though we are now piercing straight through the main axis of the Himalaya, we seldom catch even a glimpse of the snowy heights which must be so near.
But the vegetation is distinctly changing in character as we ascend—the most tropical trees and plants gradually disappearing, and more and more flowers of the temperate zone coming into evidence. And as we pierce farther into the mountains the climate becomes sensibly drier and the forest lighter. There is still a heavy enough rainfall to satisfy any ordinary plant or human being. But there is not the same deluge that descends upon the outer ridges. So the forest is not so dense. Frequently in its place social grasses clothe the mountain-sides; and yellow violets, primulas, anemones, delphiniums, currants, and saxifrages remind us of regions more akin to our own.
Now, too, we have reached the habitat of the rhododendrons, which are so peculiarly a glory of Sikkim, and it is worth while to pause and take special note of them. Out of the thirty species which are found in Sikkim, all the most beautiful have been introduced—chiefly by Sir Joseph Hooker—into England, and are grown in many parks and gardens as well as at Kew. So English people can form some idea of what the flowering trees of the Sikkim Forest are like. But they must multiply by many times the few specimens they see in an English park or hot-house, and must realise that as cowslips are in a grassy meadow, so are these rhododendron trees in the Sikkim Forest. Red, mauve, white, or yellow, they grow as great flowers among the green giants of the forest and brighten it with colour. The separate blossoms of a rhododendron tree cannot compare in beauty with the individual orchid. There is in them neither the deep richness of colour nor wonder of form nor sense of deeply matured excellence. The claim of the rhododendron to favour is rather in the collective quantity and mass of flowers so that by sheer weight of numbers it can produce its effect of colour. In some of the upper valleys the mountain slopes are clothed in a deep green mantle glowing with bells of scarlet, white, or yellow.
Perhaps the most splendid of these rhododendrons is Rhododendron grande or argenteum, which grows to a height of from 30 to 40 feet, and has waxy bell-shaped flowers of a yellowish-white suffused with pink, 2 to 3 inches long and about the same across. The scarlet R. arboreum, so general in the Himalaya, is common in Sikkim and furnishes brilliant patches of colour in the forest. And a magnificent species is R. Auchlandii or Griffithianum, which has large white flowers tinged with pink, of a firm fleshy texture and with a mouth 5 inches across. It has been called the queen of all flowering shrubs. It grows well in Cornwall, and among the hybrids from it is the famous Pink Pearl.
R. Falconeri, a white-flowered species, is eminently characteristic of the genus in habit, place of growth and locality, never occurring below 10,000 feet. In foliage it is incomparably the finest. It throws out one or two trunks clean and smooth, 30 feet or so high, the branches terminated by immense leaves, deep green above edged with yellow and ruby red-brown below. The creamy white flowers are shaded with lilac and are slightly scented. They are produced in tightly-packed clusters 9 to 15 inches across and twenty or more in numbers.
A peculiar (in that it is of all the species the only one that is epiphytal) but much the largest flowered species is the R. Dalhousiae. It grows, like the orchids, among ferns and moss upon the trunks of, large trees, especially oaks and magnolias, and attains a height of 6 to 8 feet. The flowers are three to seven in a head, and are 3 1/2 to 5 inches long and as much across the mouth, white with an occasional tinge of rose and very fragrant. In size, colour, and fragrance of the blossoms this is the noblest of the genus. It grows out-of-doors in Cornwall and in the greenhouse in other parts of England as a scraggy bush 10 to 12 feet high. R. barbatum is a tree from 40 to 60 feet high, producing flowers of a rich scarlet or blood-colour, and sometimes puce or rich pink. It is one of the most beautiful of the Himalayan rhododendrons, and is now very common in England, growing freely out-of-doors. Another truly superb plant is R. Maddeni, with very handsome pure white flowers 3 1/2 to 4 inches long and as much across the mouth. This is now a special favourite in England. It grows in large bushes in the open in Cornwall and is very sweet-scented. R. virgatum is a beautiful delicately white-flowered shrub. And R. campylo-carpum displays masses of exquisite pale yellow bells of rarest delicacy.
Besides rhododendrons, ash, walnut, and maple become more abundant as we ascend, and at 9,000 feet larch appears, and there are woods of a spruce resembling the Norwegian spruce in general appearance. Among the plants are wood-sorrel, bramble, nut, spiraea, and various other South European and North American genera.