1 8 A NATURALIST IN THE PACIFIC chap. 



it was rarely absent altogether in the inland species, a very 

 significant conclusion, as will subsequently be pointed out. 



Several other striking examples of this principle came under 

 my notice in the Pacific, and perhaps the most significant is that 

 of Scsevola, a genus of the Goodeniaceae, confined mainly to 

 Australia and the Pacific islands, but possessing also a littoral 

 species, S. Koenigii, that is found on tropical beaches all round 

 the globe. It is associated in both Hawaii and Fiji with inland 

 species, none of which are common to the two archipelagoes, and 

 in the case of the Hawaiian species not found outside the group. 

 All the species have fleshy drupes, both coast and inland plants, 

 the " stone " in the littoral species possessing a thick covering of 

 buoyant tissue, which is absent or but slightly developed in the 

 inland species. The fruits of the shore species float for many 

 months ; whilst those of the inland species experimented on by 

 me (S. Chamissoniana and S. Gaudichaudii in Hawaii, and S. 

 floribunda in Fiji) sank at once or within a few hours. Here we 

 are only concerned with the difference of buoyancy between inland 

 and littoral species. The several other questions involved con- 

 cerning this genus will be dealt with later on in this work. 



The genus Morinda offers another good example of thi.s 

 principle. It includes one widely-spread littoral species (M. citri- 

 folia), found not only in all the Pacific archipelagoes, but also over 

 much of the tropics. It is associated in all the large groups with 

 one or more inland species, some of which are endemic and others 

 more generally distributed. The littoral species displays in its 

 pyrenes a singular air-cavity, the nature of which is discussed in 

 Chapter XII., which endows them with great floating powers. 

 This cavity is not found in inland species, and the pyrenes have 

 in consequence no floating power (see Note 8). 



Calophyllum Inophyllum, an Old- World littoral tree, spread far 

 and wide over the Pacific islands, has very buoyant fruits. In the 

 groups of the South Pacific it is associated with inland species that 

 are commonly found in the forests, namely, C. spectabile and C. 

 Burmanni, the fruits of both of which, according to my observa- 

 tions in Fiji, have limited floating powers, sinking after periods 

 varying from a few days to four weeks, and lacking in great part 

 the buoyant coverings of the littoral species. Professor Schimper 

 obtained similar results with inland species from other regions 

 (Note 9). 



The fruits of the two Fijian coast trees, Barringtonia speciosa 

 and B. racemosa, possess great floating powers ; whilst those of an 



