xxvn STAGES OF THE EMERGENCE 379 



structure to the islands of Lau, that of Eua, for instance, which 

 has an elevation of 1,100 feet, being formed of reef-limestones 

 overlying volcanic tuffs. Dykes penetrate the tuffs but do not 

 enter the incrusting calcareous strata. Mr. Harker, 1 after examin- 

 ing the collections of Mr. Lister, remarks that all the rocks 

 excepting those from Falcon Island appear to be of submarine 

 formation. The volcanic material, he adds, seems to have been 

 almost exclusively of fragmental character. It would be rash, it 

 is remarked, to refer all the rocks to a Recent age, and some of 

 them may be found to go back far into Tertiary times. 



My division of the long period occupied by the emergence of 

 the Fiji Islands into two stages, the Lau stage corresponding to 

 elevations of less than 1,000 or 1,200 feet, and the Pre-Lau stage 

 which includes the earlier evidence of emergence found at heights 

 exceeding these elevations and ranging up to 2,000 or 3,000 feet, 

 may perhaps be applicable to other regions of emergence. 



As bearing on the question of the isolation and antiquity of 

 the Pacific Islands the following approximate results for the 

 Hawaiian, Fijian, and Tongan floras may be here quoted. 2 These 

 data are liable to correction ; but they are near enough to the 

 truth to be very suggestive. Of peculiar genera of flowering plants 

 and ferns the Hawaiian Islands possess about 40, the Fiji Group 

 about 16, and the Tongan Islands none. Of endemic species of 

 flowering plants there are about 80 per cent, in Hawaii, about 50 

 per cent, in Fiji, and 3 or 4 per cent, in Tonga. Granting that 

 there is much to be done yet in the investigation of these floras, 

 it would be underrating the brilliant results of the labours of 

 Hillebrand and Seemann to characterise their work as sampling. 

 Let us suppose, however, that the floras of Hawaii, Fiji, and 

 Tonga have been only sampled, the data above given would be 

 still reliable. It is quite possible to obtain a botanical equivalent 

 corresponding to the geological estimates of the relative ages of 

 these islands ; and taking the proportion of endemic plants as our 

 guide, the Lau stage, as represented by the Tongan Islands, would 

 have a value of 3 or 4, the Pre-Lau stage now exhibited in the 

 earliest stage of emergence of Vanua Levu would have a value of 

 50, and the Hawaiian stage older than all would have a value of 

 80. These results are intended as suggestive and I hope to work 



1 Geolog. Mag. June, 1891. 



2 Seemann's Flora Vitiensis, Home's Year in Fiji, Hillebrand's Flora of 

 the Hawaiian Islands, Hemsley's "Flora of the Tonga Islands" in Journal 

 Linnea?t Society, Botany, vol. 30. 



