| OCR Text |
Show 294 ISLAND LIFE. (PART l'T. The other classes of animals in St. Helena need o~cupy 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 (AJJ.qialitis sanctce-helenm )-very closely allied to a species found in South Africa, but presenting certa.in 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 ~canty 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 kincls 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 Scotlan<l, and, what is more to the point, by the fact stated by Mr. Melliss, that large seeds which have floated from Madagascar or Mauritius round the Cape of Good Hope, have been thrown on the shores of St. Helena and have then sometimes germinated ! we have therefore little difficulty in underst~nding how the island was first stocked with vegetable forms. ·when it was so stocked (generally speaking), is equally clear. For as the peculiar coleopterous fauna, of which an important fragment remains, is mainly composed of species which are specially attached. to certain groups of plants, we m·ay be sure that the plants ·were there long before the insects could establish themselves. However ancient then is the insect fauna the flora must be more ancient still. It must also be remembered that plants, when once established in a suitable climate and soil, soon CHAP. XIV.] ST. HELENA. 205 take possession of a country and occupy it almost to tho complete exclusion of later immigrants. The fact of so many European weeds having overrun Now Zealand and temperate North Arnerica may seem opposed to this statement, but it really is not so. For in both these cases the native vegetation has first been artificially removed by man and the ground cultivated; and there is no reason to believe that any similar effect would be produced by the scattering of any amount of foreign seed on ground already completely clothed with an indigenous vegetation. we might therefore conclude a p1'io?·i, that the fiora of such an island as St. Helena would be of an excessively ancient type, preserving for us in a slightly modified form examples of the vegetation of the globe at the time when the island first rose above the ocean. Let us see then what botanists tell us of its character and affinities. Tbe truly indigenous flowering plants arc about fifty in number, b~sicles twenty-six ferns. ] orty of the former and ten of the latter are absolutely peculiar to the island, and, as Sir Joseph Hooker tells us, " with scarcely an exception, cannot be regarded as very close specific allies of any other plants at all. Seventeen of them belong to peculiar genera, and of the others, all differ so markedly as species from their congeners, that not one comes under the category of being an insular form of a continental species." The afflnities of this flora are, Sir Joseph Hooker thinks, mainly African and especially South African, as indicated by the presence of the genera Phylica, Pelargoninm, Mesembryanthemum, Oteospermum, and Wahlenbergia, which. are eminently characteristic of southern extratropical Africa. The sixteen ferns which are not peculiar _are common either to Africa, India, or America, a wide range sufficiently explained by tho dust-like spores of ferns, capable of being carried to unknown distances by the wind, and the great stability of their generic and specific forms, many of those found in the Miocene deposits of Switzerland being hardly distinguishable from living species. This shows, that identity of species of ferns between St. Helena and distant countries does not necessarily imply a recent origin. The Relation of the St, Helena Compositce.-In an ebbor:1te |
