Page:Flora Hongkongensis.djvu/20

14* of similar extent known to me. The very large number of apparently endemic species,—of species only known to us from the island,—is probably occasioned by our ignorance, already alluded to, of the vegetation of continental S. China.

Another noteworthy fact apparent on the comparison of these lists, is the great preponderance of woody and long-lived plants among the species of limited areas, and of herbaceous or comparatively short-lived ones among those of a more extended range. This is, however, a general rule applicable to all Floras; for although trees and shrubs, when once in possession of the soil, tend to expel a great proportion of the herbaceous vegetation, yet the slight advantages they have in the greater power of resisting individual injury or destruction, are more than compensated by the small number of individuals, and by the slow operation of their limited means of propagation and dispersion, as compared with the countless myriads of herbs, each producing annually and widely scattering their seeds by thousands, tens or even hundreds of thousands, always ready to take possession of any land rendered vacant by the destruction of a forest into or near to which one or two individuals might have previously straggled. And when once in possession of the land, herbaceous plants, so much more capable of resisting destruction from climate or from animals than seedling trees, will often effectually prevent the re-invasion of arborescent vegetation.

In its general character, the Hongkong Flora is, as already observed, that of tropical Asia, of which it offers in numerous instances the northern limit. Taking rather more in detail the more restricted portions of the Flora, that of the damp wooded ravines of the north and west will be found to be closely allied to that of north-east India (Khasia, Assam, and Sikkim), and will probably hereafter prove to be connected with it by a gradual transition across south China; the Hongkong specimens, when specifically identical, generally showing a less luxuriant vegetation, larger flowers, and other peculiarities attributable, no doubt, to a more open situation. Other species in considerable numbers have a much more tropical character, extending with little variation over the Indian Archipelago, the Malayan Peninsula, and even to Ceylon and tropical Africa, without penetrating into the continent of India. Northwards of Hongkong the vegetation appears to change much more rapidly. Very few of the species known to range across from the Himalaya to Japan are believed to come much further south than Amoy, where, with a difference of latitude of only two degrees, the tropical features of the Hongkong Flora have (as far as we know) almost entirely