Science in Arcady. Allen Grant

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СКАЧАТЬ out of these forty plants thirty-four were to my certain knowledge of European origin. I had seen their seeds brought over by the wind or waves, and I had watched them gradually altering under stress of the new conditions into fresh varieties, which in process of time became distinct species. Two of the oldest were flowers of the dandelion and daisy group, provided with feathery seeds which enable them to fly far before the carrying breeze; and these two underwent such profound modifications in their insular home that the systematic botanists who at last examined them insisted upon putting each into a new genus, all by itself, invented for the special purpose of their reception. One almost equally ancient inhabitant, a sort of harebell, also became in process of time extremely unlike any other harebell I had ever seen in any part of my airy wanderings. But the remaining thirty new species or so evolved in the islands by the special circumstances of the group had varied so comparatively little from their primitive European ancestors, that they hardly deserved to be called anything more than very distinct and divergent varieties.

      Some five or six plants, however, I noted arrive in my archipelago, not from Europe, but from the Canaries or Madeira, whose distant blue peaks lay dim on the horizon far to the south-west of us, as I poised in mid-air high above the topmost pinnacle of my wild craggy Pico. These kinds, belonging to a much warmer region, soon, as I noticed, underwent considerable modification in our cooler climate, and were all of them adjudged distinct species by the learned gentlemen who finally reported upon my island realm to British science.

      As far as I can recollect, then, the total number of flowering plants I noted in the islands before the arrival of man was about 200; and of these, as I said before, only forty had so far altered in type as to be considered at present peculiar to the archipelago. The remainder were either comparatively recent arrivals or else had found the conditions of their new home so like those of the old one from which they migrated, that comparatively little change took place in their forms or habits. Of course, just in proportion as the islands got stocked I noticed that the changes were less and less marked; for each new plant, insect, or bird that established itself successfully tended to make the balance of nature more similar to the one that obtained in the mainland opposite, and so decreased the chances of novelty of variation.

      Hence, it struck me that the oldest arrivals were the ones which altered most in adaptation to the circumstances, while the newest, finding themselves in comparatively familiar surroundings, had less occasion to be selected for strange and curious freaks or sports of form or colour.

      The peopling of the islands with birds and animals, however, was to me even a more interesting and engrossing study in natural evolution than its peopling by plants, shrubs, and trees. I may as well begin, therefore, by telling you at once that no furry or hairy quadruped of any sort—no mammal, as I understand your men of science call them—was ever stranded alive upon the shores of my islands. For twenty or thirty centuries indeed, I waited patiently, examining every piece of driftwood cast up upon our beaches, in the faint hope that perhaps some tiny mouse or shrew or water-vole might lurk half drowned in some cranny or crevice of the bark or trunk. But it was all in vain. I ought to have known beforehand that terrestrial animals of the higher types never by any chance reach an oceanic island in any part of this planet. The only three specimens of mammals I ever saw tossed up on the beach were two drowned mice and an unhappy squirrel, all as dead as doornails, and horribly mauled by the sea and the breakers. Nor did we ever get a snake, a lizard, a frog, or a fresh-water fish, whose eggs I at first fondly supposed might occasionally be transported to us on bits of floating trees or matted turf, torn by floods from those prehistoric Lusitanian or African forests. No such luck was ours. Not a single terrestrial vertebrate of any sort appeared upon our shores before the advent of man with his domestic animals, who played havoc at once with my interesting experiment.

      It was quite otherwise with the unobtrusive small deer of life—the snails, and beetles, and flies, and earthworms—and especially with the winged things: birds, bats, and butterflies. In the very earliest days of my islands' existence, indeed, a few stray feathered fowls of the air were driven ashore here by violent storms, at a time when vegetation had not yet begun to clothe the naked pumice and volcanic rock; but these, of course, perished for want of food, as did also a few later arrivals, who came under stress of weather at the period when only ferns, lichens, and mosses had as yet obtained a foothold on the young archipelago. Sea-birds, of course, soon found out our rocks; but as they live off fish only, they contributed little more than rich beds of guano to the permanent colonising of the islands. As well as I can remember, the land-snails were the earliest truly terrestrial casuals that managed to pick up a stray livelihood in these first colonial days of the archipelago. They came oftenest in the egg, sometimes clinging to water-logged leaves cast up by storms, sometimes hidden in the bark of floating driftwood, and sometimes swimming free on the open ocean. In one case, as I recall to myself well, a swallow, driven off from the Portuguese coast, a little before the Glacial period had begun to whiten the distant mountains of central and northern Europe, fell exhausted at last upon the shore of Terceira. There were no insects then for the poor bird to feed upon, so it died of starvation and weariness before the day was out; but a little earth that clung in a pellet to one of its feet contained the egg of a land-shell, while the prickly seed of a common Spanish plant was entangled among the winged feathers by its hooked awns. The egg hatched out, and became the parent of a large brood of minute snails, which, outliving the cold spell of the Ice Age, had developed into a very distinct type in the long period that intervened before the advent of man in the islands; while the seed sprang up on the natural manure heap afforded by the swallow's decaying body, and clinging to the valleys during the Glacial Age on the hill-tops, gave birth in due season to one of the most markedly indigenous of our Terceira plants.

      Occasionally, too, very minute land-snails would arrive alive on the island after their long sea-voyage on bits of broken forest-trees—a circumstance which I would perhaps hesitate to mention in mere human society were it not that I have been credibly informed your own great naturalist, Darwin, tried the experiment himself with one of the biggest European land-molluscs, the great edible Roman snail, and found that it still lived on in vigorous style after immersion in sea-water for twenty days. Now, I myself observed that several of these bits of broken trees, torn down by floods in heavy storm time from the banks of Spanish or Portuguese rivers, reached my island in eight or ten days after leaving the mainland, and sometimes contained eggs of small land-snails. But as very long periods often passed without a single new species being introduced into the group, any kind that once managed to establish itself on any of the islands usually remained for ages undisturbed by new arrivals, and so had plenty of opportunity to adapt itself perfectly by natural selection to the new conditions. The consequence was, that out of some seventy land-snails now known in the islands, thirty-two had assumed distinct specific features before the advent of man, while thirty-seven (many of which, I think, I never noticed till the introduction of cultivated plants) are common to my group with Europe or with the other Atlantic islands. Most of these, I believe, came in with man and his disconcerting agriculture.

      As to the pond and river snails, so far as I could observe, they mostly reached us later, being conveyed in the egg on the feet of stray waders or water-birds, which gradually peopled the island after the Glacial epoch.

      Birds and all other flying creatures are now very abundant in all the islands; but I could tell you some curious and interesting facts, too, as to the mode of their arrival and the vicissitudes of their settlement. For example, during the age of the Forest Beds in Europe, a stray bullfinch was driven out to sea by a violent storm, and perched at last on a bush at Fayal. I wondered at first whether he would effect a settlement. But at that time no seeds or fruits fit for bullfinches to eat existed on the islands. Still, as it turned out, this particular bullfinch happened to have in his crop several undigested seeds of European plants exactly suited to the bullfinch taste; so when he died on the spot, these seeds, germinating abundantly, gave rise to a whole valleyful of appropriate plants for bullfinches to feed upon. Now, however, there was no bullfinch to eat them. For a long time, indeed, no other bullfinches arrived at my archipelago. Once, to be sure, a few hundred years later, a single cock bird did reach the island alone, much exhausted with his journey, and managed to pick up СКАЧАТЬ