XXVII THE ABSENTEES FROM HAWAII 375 



it grows in shallow waters along the coasts. Amongst other 

 localities where I noticed it in this group may be mentioned the 

 north-west coast of the large island of Hawaii between Kailua and 

 Keahole Point. Here in 1896 it was thriving in brackish- water 

 ponds, with Sesuvium portulacastrum growing at the edges. 

 Reinecke observes that it occurs in similar ponds in Samoa. 

 In 1897 I found it in abundance in the Rewa estuary (Fiji), both 

 in the creeks and in the main channel. In the following year 

 it was not to be found in this locality, a circumstance noticed 

 both by the natives and by resident whites. The fruits of this 

 plant possess no floating power, sinking, even after prolonged 

 drying, in a few hours. It is to ducks and to birds of similar habit 

 that its dispersal must be attributed. 



The Absentees from Hawaii. 



It has been before remarked that of the 330 or 340 genera 

 of flowering-plants recorded from Fiji some 200 are not known in 

 Hawaii. It will only be possible to deal with the absent genera in 

 a cursory manner ; but enough will be done to show that we 

 are face to face here with a multitude of the seeming inconsis- 

 tencies that so often beset the study of plant-distribution. 



A host of plants are unrepresented in Hawaii, of which it may 

 be said that their seeds or fruits are not less suited for being 

 carried across the Pacific than those of many that are now in that 

 group. On the other hand, a number of genera exist there 

 which we should never expect to have been endowed with the 

 capacity, and to have received the opportunity, of crossing nearly 

 2,000 miles of ocean. Yet perhaps when Nature acts in a whole- 

 sale fashion and excludes entire orders we may be able to perceive 

 the dim outlines of a principle of exclusion at work. But even 

 here much caution and some clearing of the ground are needed. 



For example, having regard to the several modes of dispersal 

 possessed by the great variety of fruits and seeds of the Stercu- 

 liacese, it would be almost meaningless to remark that the order 

 so well represented in Fiji is practically non-existent in Hawaii as 

 far as truly indigenous plants are concerned. It is true that 

 two species of Waltheria are here present, but one of them 

 W. americana, is a weed probably introduced by the aborigines 

 whilst the other, W. pyrolaefolia, recorded from a solitary locality 

 by the Wilkes Expedition, has seemingly never been found since. 

 From the standpoint of dispersal the genera Sterculia, Heritiera, 



