14* PREFACE. 



of similar extent known to me. The very large number of apparently 

 endemic species, — of species only known to us from the island, — is pro- 

 bably 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 her- 

 baceous vegetation, yet the slight advantages they have in the greater 

 power of resisting individual injury or destruction, are more than com- 

 pensated 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 de- 

 struction 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 pre- 

 vent the re-invasion of arborescent vegetation. 



In its general character, the Hongkong Flora is, as already ob- 

 served, 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 Hong- 

 kong specimens, w r hen specifically identical, generally showing a less luxu- 

 riant 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. North- 

 wards 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 fea- 

 tures of the Hongkong Flora have (as far as we know r ) almost entirely 



