xix THE PHYSICAL CONDITIONS 207 



occur. These three groups lie near the three angles of the tri- 

 angular area of the Pacific over which the various archipelagoes 

 are scattered. They are thus geographically well placed for an 

 inquiry into the subject of plant-dispersal over this ocean, and 

 each of their floras has been investigated by botanists of various 

 nationalities — American, Austrian, British, French, German, and 

 Italian. The Fijian area may be regarded as including the adjacent 

 Samoan and Tongan groups, though the individual group or the 

 whole area will always be in this work particularised. In the same 

 way Tahiti will be viewed as usually representative of the larger 

 islands of the surrounding groups of the Cook and Austral Islands 

 and of the Marquesas ; and under the designation of the Tahitian 

 area or Tahitian region there will be generally included the 

 Paumotu archipelago. 



Comparison of the Areas and Altitudes of Hawaii, 



Fiji, and Tahiti. 



Since differences in physical conditions have played an impor- 

 tant part in plant distribution in these groups — such, for instance, 

 as in determining the development of a mountain flora or in 

 favouring the relative abundance of particular types of plants — 

 it is at first essential to obtain a general idea, in the case of the 

 larger islands of each group, of their size and elevation, and of 

 the more conspicuous differences in their climates. 



Hawaii, the largest island of the Hawaiian archipelago, has an 

 area of 4,210 square miles. All the other islands of the group are 

 considerably smaller — Maui, the second in size, having a surface of 

 760 square miles ; Oahu coming next ; and after it Kauai, with an 

 area of 590 square miles. The area of Viti Levu, the largest 

 island of the Fijis, is 4,112 square miles, being thus closely similar 

 to that of the island of Hawaii ; Vanua Levu, the second in size, 

 is 2,433 square miles in extent ; whilst the other important islands 

 of the group are much smaller, Taviuni, the third in size, having 

 an area of 218, and Kandavu an area of 125 square miles. Tahiti, 

 the largest and loftiest island of Eastern Polynesia, has a surface 

 of about 400 square miles ; whilst most of the other elevated 

 islands of the groups around are considerably smaller. 



In respect of elevation above the sea, there is a great contrast 

 between the islands of these three regions. Taking the Hawaiian 

 Group first, we notice that the three principal mountains of the 

 large island of Hawaii rise in the cases of Mauna Kea and Mauna 



