CHAP. XV'.] 



THE SANDWICH ISLANDS. 



309 



(comprising about ten thousand species), its distinctness from all 

 others, the great specialisation of its flowers to attract insects, 

 and of its seeds for dispersal by wind and other means, we can 

 hardly doubt that its origin dates back to a very remote epoch. 

 We may therefore look upon the Compositoe as representing the 

 most ancient portion of the existing flora of the Sandwich Islands, 

 carrying us back to a very remote period when the facilities for 

 communication with America were grea,ter than they are now. 

 This may be indicated by the two deep submarine banks in the 

 North Pacific, between the Sandwich Islands and San Francisco, 

 which, from an ocean floor nearly 3,000 fathoms deep, rise up to 

 within a few hundred fathoms of the surface, and seem to indi- 

 cate the subsidence of two islands, each about as large as Hawaii. 

 The plants of North Temperate affinity may be nearly as old, but 

 these may have been derived from Northern Asia by way of 

 Japun and the extensive line of shoals which run north-west- 

 ward from the Sandwich Islands, as shown on our map. Those 

 which exhibit Polynesian or Australian affinities, consisting for 

 the most part of less highly modified species usually of the same 

 genera, may have had their origin at a later, though still some- 

 what remote period, when large islands, indicated by the exten- 

 sive shoals to the south and south-west, offered facilities for the 

 transmission of plants from the tropical portions of the Pacific 

 Ocean. 



Antiquity of tlie Haivaiian Famia and Flora. — The great anti- 

 quity implied by the peculiarities of the fauna andflora, no lessthan 

 by the geographical conditions and surroundings, of this group, 

 will enable us to account for another peculiarity of its flora — 

 the absence of so many families found in other Pacific Islands. 

 For the earliest immigrants would soon occupy much of the 

 surface, and become specially modified in accordance with the 

 conditions of the locality, and these would serve as a barrier 

 against the intrusion of many forms which at a later period 

 spread over Polynesia. The extreme remoteness of the islands, 

 and the probability that they have always been more isolated 

 than those of the Central Pacific, would also necessarily result in 

 an imperfect and fragmentary representation of the flora of 

 surrounding lands. 



