XIV LITTORAL AND INLAND PLANTS' RELATIONSHIP 137 



of Ipomea of the Pacific islands to connect them with the coast 

 species. They are all widely ranging species, and their seeds have 

 been carried to the islands, each in its own fashion. So again with 

 the inland species of Hibiscus found in the Polynesian islands and 

 often cultivated, we cannot either from the point of view of 

 dispersal or of affinity connect them with the far-ranging littoral 

 species, H. tiliaceus, which belongs to a section of the genus 

 distinct from those sections to which the inland species belong. 



In a similar way there is no ground for supposing that Cordia 

 aspera, an inland species confined to Fiji, Tonga, and Samoa, is 

 derived from C. subcordata, the widely distributed littoral species 

 of the Pacific and of the Old World, since they belong to different 

 sections of the genus. But, apart from any question of affinity, 

 the drupes of inland species of Cordia are known to be well suited 

 for dispersal by frugivorous birds, though, unlike the littoral species 

 above named, not adapted for transportal by the currents. The 

 genus Vitex, which is represented by a wide-ranging littoral species 

 in the Pacific (V. trifolia), appears to be associated with inland 

 species only in Fiji, where one or two, seemingly endemic, occur, 

 But there is nothing in Dr. Seemann's description of V. vitiensis, one 

 of these species, that at all suggests its derivation from the strand 

 species, a very variable plant that often extends far inland into the 

 plains, adopting a different habit of growth in those localities. It 

 is known that Vitex fruits can be dispersed both by birds and by 

 currents. This genus is more fully discussed in a later chapter. 



Of the genus Colubrina there seem to be only two Pacific 

 species known — one the widely distributed shore-plant, C. asiatica, 

 a straggling shrub with 'alternate leaves found in all the Pacific 

 groups and on the beaches of much of the tropics of the Old 

 World ; the other a tree, C. oppositifolia, with opposite leaves, that 

 is peculiar to the Hawaiian islands, where it frequents the open- 

 wooded and scrubby inland districts. The seeds of the shore- 

 plant float unharmed for many months, whilst the fruits of the 

 inland plant, which differ in some important respects (see Note 52), 

 would float only for a week or two. The strand species is also quite 

 at home inland in many parts of the world ; and there is nothing 

 from the standpoint of affinity to indicate that in Hawaii it has 

 given birth to an inland species so divergent in habit and in 

 character. There is of course the difficulty of explaining how a 

 plant like C. oppositifolia, with such a dry, unattractive fruit, could 

 be indebted to birds for its original introduction into the group ; 

 but the same difficulty arises with a host of Hawaiian plants. It 



