i INTRODUCTION 7 



of the Andes, or in the lowlands of Fuegia. Other plants that I 

 have not mentioned, such as Coprosma, would bring back to him 

 New Zealand. He might even be on a mountain-top in Central 

 Africa, or on a Madagascar plateau ; whilst in the boggy region of 

 an elevated Hawaiian tableland he would meet with not only the 

 physical conditions, but also several of the plants found on the 

 higher levels of Tristan da Cunha. 



It is, however, to be noted that although these mountain-tops 

 in the mid-Pacific have been stocked with genera from the four 

 quarters of the compass, the species as a rule are restricted to that 

 particular archipelago. Whilst the beach and the river in most 

 cases possess plants that have very wide ranges over the earth, a 

 good proportion of the species on the mountain-summit are not 

 found elsewhere. This implies a partial suspension of the meansU 

 of dispersal on the mountain-top, whilst the currents and waterfowl ' 

 are still actively distributing the seeds of the littoral tree and of 

 the aquatic plant. We here get a foreshadowing of another great 

 principle, or of another line along which Nature has worked in 

 stocking these islands of the Pacific with their plants, a subject 

 concerning which much will be said in later pages. 



Hitherto, we have dealt only with a small proportion of the 

 flora, and with but a small portion of the area of the island. We 

 have yet to deal with the intermediate region between the sea- 

 border and the summit of the island, or, in other words, with 

 the forested mountain slopes. This is the home of many of the 

 peculiar species and peculiar genera, both of plants and birds ; and 

 it is with this zone that we shall be mainly concerned when 

 we come to contrast the floras of the several archipelagoes of the 

 tropical Pacific. Here the agencies of dispersal have, to a large 

 extent, ceased to act ; and the question will arise as to the connec- 

 tion between the endemic character of the plants and the endemic *" 

 character of the birds. We shall have to ask why this island, after 

 receiving so many plants, ceased to be centres of dispersal to other 

 regions. It is possible that these seeds or fruits have lost their 

 capacity for dispersal ; but only a few instances of this change 

 present themselves. Rather it may be supposed that the birds 

 that originally brought the seeds to the island came to stay ; and 

 this at once suggests another query as to the cause of the change 

 of habit. I am alluding here not to the plants with minute seeds, 

 such as Sagina and Orchis, which Mr. Wallace, in his Darwinism, 

 regards as capable of being transported by strong winds over 

 a thousand miles of sea ; but to those numerous plants found in 



