250 



DISTRIBUTION OF PLANTS. 



up out of the ocean to its present elevation. During the geological 

 Period now pending, and termed " Alluvial, " this vast mass of coral- 

 limestone had formed in the sea; its emerging even, being at an epoch 

 too remote for the memory of man. 



From the boat, vertical and vein-like fissures were observed in the 

 face of the clilF; but more conspicuous at different elevations, were 

 some perfectly horizontal lines of open-mouthed caves, seeming as 

 though formed by the action of surf; if really so, the rising above the 

 the ocean must have been gradual, or at least at successive epochs. 



On close examination, the imbedded shells and fragmentary corals 

 were found to be the same throughout, from the top of the cliff to the 

 base ; and all of them belonging to existing species. Independent of 

 the marine species, Mr. Dana found ''some imbedded land shells, 

 Bulimi;" perhaps entangled by the percolation of rain-water; for 

 stalactites were observed in the above open-mouthed caves. Living 

 land sJiells were, however, met with by Mr. Couthouy ; and though 

 minute, have proved peculiar species. The only instance of the kind 

 we met with on coral islands : but it has been already stated, that the 

 question of the contemporaneous origin of species may, perhaps, be 

 one day solved on Metia. 



Vatu-lele, the other elevated coral-island seen during our Voyage, 

 is in the close vicinity of rocky islands ; and will be described in the 

 account of the Feejeean Group. 



The Vegetable Groavth. I met with no marks of torrents on 

 Metia, nor witli running water, nor even with springs; yet the soil 

 was kept sufficiently moistened by the rains, for the production of 

 large trees and a luxuriant forest-growth : much of which had been 

 cleared away, at difierent times, for the purposes of cultivation. 



In the absence of mineral soil, the flora proved chiefly interesting 

 from the presence of many rocky-island species. Of the plants we met 

 with, the Capparis and Aspidkim were not seen elsewhere; of the re- 

 mainder, the rocky-island species were all found subsequently either 

 on Aimeo or Taheiti ; while some coral-island species were growing on 

 Metia, that did not occur on any other high island. This will appear 

 by the following List : 



Lepidium ; bis (No. 1 Paumotuan) coraLisIands.* 

 Capparis (No. 1) ; decumbent. Growing near the beach. 



(Cardamine sarnientosa, Forst. ; No. 1). Humble; leaves pinnatisect, mostly radical; 

 flowers having a purple tinge. (Afterwards seen on Taheiti.) 



