122 



A NATURALIST IN THE PACIFIC chap. 



their adaptations to littoral life, especially if those adaptations are 

 not conflicting with the conditions of life beyond the littoral 

 zone, and if the cf tmpetition does not require special adaptations." 



My view, however, is that any process of adaptation is 

 unnecessary. All these plants, it is contended, were originally 

 inland plants that acquired the buoyant qualities of their seeds and 

 fruits in the inland stations, and ultimately found a station at the 

 coast through the sorting process above referred to. In the case of 

 plants like Ipomea pes caprae and Cassytha filiformis this would 

 be conceded, since they belong to the acknowledged non-adaptive 

 groups discussed in the preceding chapter. It is only to some of 

 these plants, such as Scsevola Koenigii and Cerbera Odollam, that 

 the adaptation view of Professor Schimper is applied ; and the 

 question arises whether we are justified in making such a distinction, 

 or, in other words, whether it is antecedently probable that two 

 independent principles have been at work in determining the 

 fitness of seeds and fruits for dispersal by the currents. 



The plants for which the influence of adaptation through Natural 

 Selection is claimed belong, as stated in Chapter XII., almost 

 entirely to the third group. It is admitted that with the other two 

 groups the utmost that any sorting or selecting process would effect 

 would be to determine a station at the coast and to extend the area 

 of distribution. The numerical aspect of the question therefore 

 acquires some importance ; and the reader's attention is accordingly 

 directed to the results tabulated in Note 45, where it is shown 

 (assuming for the time that there is no difference of opinion 

 about the adaptive significance of the seeds and fruits concerned) 

 that the plants of the third or adaptive group make up only about 

 half the total. It would therefore appear that if the agencies of 

 Natural Selection have been at work here either in bettering or 

 in developing buoyant structures, half of the shore-plants with 

 buoyant seeds or fruits have not come within their influence. 



But the subject takes another aspect when we reflect that in 

 some buoyant fruits, as with Ximenia americana and Calophyllum 

 inophyllum, the two principles would seem to have been at work. 

 Whilst from this standpoint Natural Selection is regarded as 

 having either developed or increased in amount the layer of 

 buoyant tissue in the fruit-coats, the buoyant kernels are not viewed 

 as adaptive in their origin. In the case of Ximenia americana the 

 dispersing agency of frugivorous birds adds another factor, since, 

 as before stated, its drupes are known to be dispersed by fruit- 

 pigeons. In the cases of Sca^vola Koenigii and of Vitex trifolia. 



