10 A NATURALIST .IN THE PACIFIC chap. 



But true as this may be, the composition of a strand-flora is a 

 very complex one. Although, as Prof. Schimper remarks, the 

 mangrove formation is more isolated than the beach formation, and 

 affords evidence of a much earlier separation, the beach-plants as a 

 body are anything but homogeneous in their character. Their 

 physiognomy varies to some extent with the alteration in the 

 characters of the inland flora, changes to which the mangrove 

 formation makes a very slow response. Yet amongst the plants of 

 the beach we find strangely assorted forms that are as ancient 

 denizens of the coast as the mangroves themselves. Take, for 

 instance, Salsola Kali, that thrives alike on a beach in Chile, on the 

 sea-shore in Devonshire, and in the salt-marshes of the interior of 

 Tibet. Then, again, there is a type of littoral plant, of which 

 Armeria vulgaris and Plantago maritima may be taken as examples, 

 which is equally at home on the beach and on the tops of inland 

 mountains. We might in a sense apply the wrecker's motto, 



" What the sea sends and the land lends," 



to the history of a littoral flora. Yet on the other hand the inland 

 flora in its turn receives a few recruits from the littoral flora ; and 

 it is the relation between the inland and coast species of the same 

 genus that offers one of the most fascinating studies in the botany 

 of the Pacific Islands. 



This introductory chapter may be concluded with a few 

 remarks on what may be termed " the ethics of plant-dispersal." 

 Not that this is in any way a suitable phrase, but it best expresses 

 my sense of the lack of propriety in some things connected with 

 this subject. It is odd, for instance, that we speak of the dispersal 

 of plants and animals in the same breath, as if the process was in 

 both cases identical. Seeing that from this point of view we judge 

 a plant only by its seeds and fruits, it is apparent that we are 

 following quite a different method than that which we employ in 

 the study of the dispersal of animals. Whilst the zoologist 

 classifies the units of dispersal, the botanist does nothing of the 

 kind ; and the two systems of classification are at the outset 

 fundamentally distinct. The student of plant-dispersal thus often 

 finds himself placed in an awkward dilemma. For him a family is 

 a collection of allied genera having similar seeds or fruits and 

 fitted often for the same mode of dispersal. A family like 

 Sterculiaceae, possessing such a variety of seeds and fruits suitable 

 for very different modes of dispersal, is from his standpoint a 

 collection of dissimilar units. Genera like Commersonia, 



