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Show 3G4 GEOGRAPHICAL DISTRIBUTION, CII.A.P. XL years, it would I think be a. marvellous fact if n1any plants had not thus become widely transpor~ed. These means of transport are sometimes called accidental, but this is not strictly correct: the currents of the sea are n:ot accidental, nor is the direction of prevalent gales of wind. It should be observed that scarcely any means of transport would carry. seeds. for. ve~y great distances· for seeds do not retain theu vitality when exposed f~r a great length of time t~ th~ action of seawater ; nor could they be long carried In the crops or intestines of birds. These means, however, would suffice for occasional transport across tracts of sea some hundred miles in breadth, or from island to island, or from a continent to a neighbouring island, but not from one distant continent to another. The floras of distant continents would not by such means become mingled in any great degree; but would remain as distin~t as we now see them to be. The currents, from theu course, would never bring seeds from North America to Britain, though they might and do bring seeds from the West Indies to our western shores, where, if not killed by so long an immersion in salt-water, they could not endure our climate. Almost every year, one or two land-birds are blown ~cross the whole Atlantic Ocean, from North AmeriCa to the western shores of Ireland and England ; but seeds could be transported by these wanderers only by ~ne means, namely, in dirt sticking to their feet, whiCh is in itself a rare accident. Even in this case, how small would the chance be of a seed falling on favourable soil, and coming to maturity! But it would be a great error to argue that because a we~l-stocked island like Great Britain, has not, as far as IS known (and it would be very difficult to prove thi_s), received within the last few centuries, through occaswnal means CHAP. XI. DURING THE GLACIAL PERIOD. 065 of t::ansport, immjgrants from Europe or any other continent, that a poorly-stocked island, though standing more remote from the mainland, would not receive colonists by similar means. I do not doubt that out of twenty seeds or animals transported to an island even if far less well-stocked than Britain, scarcely mor~ than one would be so well fitted to its new home, as to becom~ naturalised. But this, as it seems to me, is no v~lid argument against what would be effected by occasw.nal ~eans o~ transp?rt, during the long lapse of geological time, whilst an Island was being upheaved a~d ~orme~, and before it had become fully stocked w1th Inh.abit~nts. On almost bare land, with few or no destructi.ve Insects or birds living there, nearly every seed, whwh chanced to arrive, would be sure to germinate and survive. IJlspersal during t~e Glacial period.-The identity of many plants and animals, on mountain-summits, separated from each other by hundreds of miles of low~ ands, where the Alpine species could not possibly exist Is o:r~e o~ ~he most striking cases known of the sam~ spec~e~ .hving at .distan~ points, without the apparent possibility of therr having migrated from one to the other. It is indeed a remarkable fact to see so many of the same plants living on the snowy regions of the Alps or Pyrenees, and in the extreme northern parts of Europe; ~ut .it is far more remarkable, that the plant~ on the White Mountains, in the United States of Amenca, are all the same with those of Labrador and nearly all t?e same, as we hear from Asa Gray, with those on the loftiest mountains of Europe. Even as long aao as 17 4 7' such facts led Gmelin to conclude that the same spe~ie~ must have been independently created at several distinct points ; and we might have remained |