8o PLANT GEOGRAPHY 



akin to the flora of Fuegia than to that of the nearer 

 African continent; and New Zealand, out of 935 species 

 of Spermatophytes, has 677 endemic, 222 with Australian 

 and in with American affinities. This last example 

 illustrates the fact that the flora of an island is generally 

 derived from more than one source. Even the British 

 Isles, with a flora mainly " Germanic," or Central 

 European, has Alpine species connected rather with 

 Scandinavia, and at least one species (Eriocaulon 

 septangulare With.) of American origin. 



While continental islands will start with a flora com- 

 posed of continental species, oceanic islands, beginning 

 with no plants at all, will be gradually occupied by those 

 which have the best means of dispersal. Low-lying 

 coral islands will be mainly stocked by ocean-borne 

 strand-plants; but volcanic islands, like Krakatau, will 

 simultaneously receive, at higher levels, wind-borne and 

 bird-borne species. The dependences of oceanic islands 

 on occasional or accidental methods of introduction has 

 a marked effect upon their floras. They are generally 

 rich in species of Ferns, Mosses, and other Cryptogams, 

 the excessively minute spores of which lend themselves 

 to wind-dispersal. Whole tribes of plants, such as those 

 with large and heavy seeds, are often absent. Not only 

 is the total number of species smaller than on corre- 

 sponding continental areas, but the proportion of species 

 to genera is small, many genera being monotypic 

 represented, that is, by a single species. So, too, the 

 proportion of genera to orders is small. This im- 

 poverished character of the flora lessens the intensity of 

 the struggle for existence, so that ancient races " living 

 fossils," as they have been termed may survive on 

 islands when they have been exterminated elsewhere. 



When the endemic species or genera " represent " 

 those of the mainland, resembling them, that is, without 

 being identical with them, it appears probable that they 

 have originated in the island by modification of the 

 continental type; and the degree of this modification 

 whether specific or generic affords some evidence as to 

 the antiquity of their origin. 



In tropical and sub-tropical islands the effect of the 

 insular climate is seen in the prevalence of woody, 

 shrubby, and evergreen forms; whilst in those of higher 

 latitudes herbaceous perennials predominate. Annual 



