XXII THE TREE-LOBELIAS 257 



in Rarotonga at elevations of 1,000 to 1,500 feet, but it was rare 

 and has not yet been described. The other genus, Apetahia, has 

 only been recorded from Raiatea, where it is represented by a 

 solitary species (6 feet high) growing, according to Nadeaud, in the 

 mountains of that island. 



It is apparent that the dispersal of these genera of the Lobe- 

 liacese amongst the groups of Eastern Polynesia ceased long ago. 

 From the circumstance that Sclerotheca exists in Tahiti and in 

 Rarotonga, which are about 650 miles apart, it may be inferred 

 either that the genus was introduced into this region from outside, 

 or else, which is perhaps more probable, that it was developed in 

 Tahiti whence it was transported to Rarotonga. Hemsley speaks 

 of this Tahitian genus as seemingly marking a former wide exten- 

 sion of the Hawaiian arborescent type of the Lobeliacese {Introd. 

 Bot. Chall. Exped., p. 68). This is the view that will be adopted 

 in this chapter, and it is precisely the view advocated by Bentham 

 and followed here, in the case of the early Compositse of the 

 Pacific. 



With regard to the absence of these arborescent Lobeliaceae 

 from the island-groups of the Western Pacific, and notably from 

 Fiji and Samoa, where no members of the order seem to occur, it 

 is probable that, as in the case of the similar distribution of the 

 early Composit£E described in the preceding chapter, this is to be 

 attributed to the fact that the Western Pacific archipelagoes were 

 more or less submerged during the general dispersion of the Com- 

 positse and Lobeliaceae over the Pacific in the earliest age of 

 the floral history of these islands. The occurrence of the early 

 Compositse and Lobeliaceae in Rarotonga, which is almost half- 

 way between Tahiti and Tonga on the outskirts of the Fijian 

 region, sufficiently indicates that they are not lacking in that region 

 from inability to reach there in the past. During the age of 

 general dispersal of these two orders over the Pacific, probably 

 only a few rocky islets, tenanted perhaps by Conifers, marked the 

 situation in the Tertiary period of the present archipelagoes of 

 Fiji and Samoa. 



One may note in passing the general absence of these arbor- 

 escent types of the Lobeliaceae from Malaya, since they do not 

 seem to have been recorded either from the Owen Stanley Range 

 in New Guinea or from Kinabalu in North Borneo, the highest 

 mountain in the Malayan Islands, or from the mountains of Java. 



The consideration of the occurrence of these plants in other 

 tropical or subtropical oceanic islands need not detain us long, 

 VOL. II S 



