THE FACTORS OF DISTRIBUTION 79 



Japan, or the Philippines, are on submerged plateaux, 

 seldom more than 100 fathoms below sea-level; while 

 the ancient examples, such as Madagascar, the Greater 

 Antilles, Iceland, Celebes, and New Zealand, are usually 

 separated from the mainland by water of a thousand 

 fathoms, or more, in depth, and may have a considerable 

 proportion of " endemic " species or genera, i.e. of forms 

 peculiar to them. 



Oceanic islands, on the other hand, are generally 

 remote from any continent; are either volcanic or 

 coralline in structure and origin; surrounded by deep 

 sea; and inhabited by a flora that is small in its total 

 number of species, but has a large percentage of endemic 

 types. The existence of these endemic types illustrates 

 the importance of geographical isolation as a factor in 

 the production of new forms. If only species, and not 

 genera, are endemic, it seems probable that the origin of 

 the island, or its covering with vegetation, does not 

 date back very far. If they are of generic rank, such as 

 the Double Coco-nut (Lodoicea) of the Seychelles, it may 

 be more ancient. At the same time such forms are not 

 altogether isolated. Lodoicea is related to the genus 

 Borassus, Palms native to the continental regions of 

 Africa and India. The most isolated type, perhaps, is 

 Lactoris fer nandeziana Phil., a genus and species endemic 

 to Juan Fernandez, which has been made the sole type of 

 a distinct Order. The rest of the flora of Juan Fernandez 

 has, on the whole, a distinct Chilean facies; and the 

 endemic forms of all oceanic islands show some con- 

 tinental affinities, while the non-endemic plants are, of 

 course, common to some other land. This is not, 

 however, always the nearest land, nor that from which 

 ocean-currents or prevalent winds now come. In the 

 Galapagos Archipelago almost every island has its own 

 endemic species; the islands nearer to South America 

 have forms more nearly allied to those on the mainland, 

 while islands between others in position produce species 

 intermediate in their characters. Affinity with a more 

 distant land suggests that migration may have taken 

 place at a more or less remote Tertiary period, when 

 winds, currents, the outlines of continents, or the 

 presence of intervening islands may have been different 

 from what it is at present. Whilst the Galapagos flora 

 is completely American, that of Kerguelen Land is more 



