CHAP, xiy 



ST. HELENA 



305 



water-cress, one or two species of Cyperus, and the 

 Australian Isapis prolifera. The same absence of fresh- 

 water shells characterises the Azores, where, however, there 

 is one indigenous water-beetle. In the Sandwich Islands 

 also recent observations refer to the absence of water- 

 beetles, though here there are a few fresh-water shells. It 

 would appear therefore that the wide distribution of the 

 same generic and specific forms which so generally 

 characterises fresh-water organisms, and which has been 

 so well illustrated by Mr. Darwin, has its limits in the very 

 remote oceanic islands, owing to causes of which we are at 

 present ignorant. 



The other classes of animals in St. Helena need occupy 

 us little. There are no indigenous mammals, reptiles, 

 fresh-water fishes or true land-birds ; but there is one 

 species of wader — a small plover {JEgialitis scmctoe-helenm) 

 — very closely allied to a species found in South Africa, but 

 presenting certain differences which entitle it to the rank 

 of a peculiar species. The plants, however, are of especial 

 interest from a geographical point of view, and we must 

 devote a few pages to their consideration as supplementing 

 the scanty materials afforded by the animal life, thus 

 enabling us better to understand the biological relations 

 and probable history of the island. 



Native Vegetation of St. Helena. — Plants have certainly 

 more varied and more effectual means of passing over wide 

 tracts of ocean than any kinds of animals. Their seeds are 

 often so minute, of such small specific gravity, or so 

 furnished with downy or winged appendages, as to be 

 carried by the wind for enormous distances. The bristles 

 or hooked spines of many small fruits cause them to 

 become easily attached to the feathers of aquatic birds, and 

 they may thus be conveyed for thousands of miles by these 

 pre-eminent wanderers ; while many seeds are so protected 

 by hard outer coats and dense inner albumen, that months 

 of exposure to salt water does not prevent them from 

 germinating, as proved by the West Indian seeds that 

 reach the Azores or even the west coast of Scotland, and, 

 what is more to the point, by the fact stated by Mr. 

 Melliss, that large seeds which have floated from 



X 



