DISTRIBUTION IN DIFFERENT PARTS OF THE GLOBE. 673 



In speaking of the floras of comparatively small (and usually volcanic) 

 islands in the midst of the ocean, and at a distance from continents, 

 Dr. Hooker remarks : — " They are rich in Perns, Mosses, and other 

 flowerless plants, and they possess many evergreen, but comparatively 

 few herbaceous plants, and fewer or no' indigenous annuals. Plants 

 which are herbs on continents often either themselves become shrubby 

 on islets, or are represented by allied species that are shrubby or 

 arborescent. Species are few in proportion to genera, and genera in 

 proportion to orders. The mountains, however lofty, present few 

 alpine or sub-alpine species ; and the total number of species is usually 

 small compared with what continental areas of equal size and similar 

 conditions contain. The floras of islands all display an affinity with 

 one another, or with certain continents ; as is shown by Madeira, the 

 Azores, and Canaries, containing many plants in common that are not 

 found on any continent ; by the Oanarian flora being in the main a 

 Mediterranean one; the St. Helena being an African, and so on." 

 The conclusions he comes to are as follows : — 



1. The Flora of no oceanic island is an independent one ; in all cases it is 

 quite manifestly closely allied to some one continental Flora, and however distant 

 it may tie from the mother continent, and however much it may approximate to 

 another continent, it never presents more than faint traces of the vegetation of 

 such other continent. Thus the Azores, though 1000 miles nearer to America 

 than Madeira is, has not even so many American types as Madeira has. St. 

 Helena, though 1000 miles nearer to South America than is any part of the 

 African coast, contains scarcely any plants that are even characteristic of America ; 

 and Kerguelen's Land, though far more distant from Tierra del Fuego than it is 

 from Africa, Australia, or New' Zealand, is almost purely Fuegian in its Flora. 



2. The Floras of all these islands are of a more temperate character than those 

 of the mother continents in the same latitude ; thus, Madeira and the Canaries 

 have a MediteiTanean Flora, though they are respectively 5° and 10° south of the 

 principal parallel of the Mediterranean region ; the affinities of the St. Helena 

 Flora are strongly South African ; and the Flora of Kerguelen's Land, in lat. 48°, 

 is what we might expect to meet with in Fuegia, were the American continent 

 produced southward to lat. 60°. 



3. All contain many and great peculiarities, distinguishing them from the 

 continental Floras ; and these admit of the following classification : — 



o. Plants peculiar to the islands and hetraying no affinity with those of the 

 mother continent, as the Laurels, etc. , of Madeira and the Canaries and Azores ; 

 the arhoresoent Composite of St. Helena, and the Kerguelen's Land Cabbage. 



^. They contain certain genera that are very different from those of the 

 mother continent, but are evidently allied to them ; and others but slightly 

 different. They contain species that are very different from, but allied to, those 

 of the mother continent ; and others that are but slightly different from con- 

 tinental ; and they contain varieties in the same categories. 



4. As a general rule, the species of the mother continent are proportionally 

 the most abundant, and cover the greatest surface on the islands. The peculiar 

 species are rarer, the peculiar genera of continental affinity are rarer still ; whilst 

 the plants having no affinity with those of the mother continent are often very 

 common, in the temperate islands especially — at least under the conditions which 

 the island vegetation now presents. 



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