by Grant Allen
When the glaciation was at its worst in the northern hemisphere, almost the entire surface of the European continent, from Scandinavia and Lapland, to England, Belgium, and central Germany, lay buried beneath one unbroken sheet of permanent ice. But when the conditions were a little less severe, local glaciers radiated from the chief mountain bosses of Scotland, Wales, and the Isle of Man, and ground these deep grooves and scratches on the worn surface of the denuded rock. At length the climate began to mend slightly; and then the plants and animals of the Arctic zone spread uninterruptedly over the whole of northern Europe, from the limit of pack-ice to at least the southern slope of the Alps on the Italian side. Remains of these glacial animals — Arctic lemmings, musk sheep, white hares, reindeers, Alpine marmots, and snowy owls — are still found among the bone-caves and river drift of the interglacial ages in various parts of Europe, from Scandinavia to the Tuscan grottoes. At the same time we may be pretty sure that high Arctic or Alpine plants, adapted to a chilly climate, like the saxifrages, the sibbaldia, the crowberry, and the Swiss veronica, spread over all the plains and valleys of Great Britain and the neighbouring continent.
In those days, we saw good reason to believe when we were examining the stranded southern flora of Cornwall and Devonshire, England and Ireland were united to one another as well as to France and Holland by a broad belt of lowland occupying what is now the bed of the two channels and the German Ocean, so that the mammoth and the cave-bear could roam uninterruptedly from the Yorkshire hills to the rock-shelters of the Dordogne, and from the bogs of Connaught to the then ice-clad summits of the Hartz and the Jura. The dark hunters of the period, who framed the rough, chipped stone hatchets of the Abbeville drift and the beautiful flint arrowheads of the southern French caves, could in like manner range without let or hindrance from Kent’s Hole at Torquay to the Schwatka cavern in Moravia, and from the honeycombed cliffs of Yorkshire valleys to the limestone grottoes among the Alpine slopes. That distribution of land and water easily accounts for the dispersion of Arctic and snow-line plants or animals over all the snowy regions of northern Europe.
But as the cold began to subside, and as a warmer fauna and flora invaded the now milder plains and valleys of central Europe, the glacial types, being less adapted to the new conditions, began to retreat northward towards the Arctic Circle, or upward towards the chilly summits of the principal mountains. Slowly, age after age, the southern plants and animals overran all the lower portions of the continent, cutting the glacial fauna and flora in two, and established themselves as far as the outlying peninsula of Britain, which still continued to form an integral part of the European mainland. After most of the Germanic types had made good their foothold even in this distant region, however, and after the still more southern pæonies of the Steep Holme and the rock-cistus of Torquay had established themselves under the lee of the Cornish and Kerry mountains, on the submerged tract which then stretched out far to the west of the Scilly Islands, the land began to sink slowly toward sea-level; and at last an arm of the Atlantic encircled the whole of Ireland, and still later the waters of two long gulfs which now form the English Channel and the North Sea met together by bursting through the narrow barrier of chalk between Dover and Cape Blancnez. Thus Britain finally became an island group; and, being washed on three sides by the warm current of the Gulf Stream, it acquired an unusually high and equable temperature for a district situated so far to the north and rising into so many chains of low mountains. But not all the plants and animals which inhabit the continent had had time to reach England, which has a comparatively poor fauna and flora; while still more failed to get to Ireland before the separation; and so, the Irish flora contains a larger proportion of Spanish and Portuguese types, while the mass of the English flora, especially in the eastern half of the island, is essentially Germanic.
Even after this change to more genial conditions, however, many of the Arctic plants, though now separated by wide stretches of sea or land from their nearest relatives elsewhere, managed to keep up a vigorous existence in the Scotch Highlands, the Welsh hills, and the greater summits of the Lake district. Some of them still cover vast tracts of country in the north; as, for example, the little green sibbaldia, a tufted Arctic trailer, whose herbage forms a chief element of the greensward in many parts of the Highlands; or the pretty eight-petalled dryas, which stars with its sweet white blossoms the limestone rocks of northern England and the Ulster hills. Among the more common of these isolated old glacial flowers in Britain are the Alpine meadow-rue, the northern rock-cress, the Arctic whitlow-grass, the Alpine pearlwort, the Scottish asphodel, the mossy cyphel, the mountain lady’s mantle, the purple saxifrage, and the red bearberry. Altogether, we have still more than two hundred such Alpine or Arctic plants, stranded among our uplands or in the extreme north of Scotland, and probably separated for many thousand years from the main body of their kind in the Arctic Circle or the snowy mountains of central Europe.
Our pretty little Lloydia here is far rarer in Britain than these low mountain kinds; for it has died out utterly even in Scotland itself, and now survives nowhere with us except on these solitary Welsh summits. Such cases are frequent enough in Britain; for while the moderate mountainous or Arctic species still go on thriving among the straths and corries, the coldest kinds of all have often been pushed upward and ever upward by the advancing tide of southern flowers till they are left at last only on a few isolated mountain tops, where many of them are even now in course of slowly disappearing before the steady advance of the southern types. For example, there is a certain pretty kind of heath, confined to northern or Arctic hill-sides, which till lately lingered on in Britain only on the one mountain known as the Sow of Athole in Perthshire; but of late years it has grown rarer and rarer with each succeeding summer, until it is now probably quite extinct. It is the natural tendency of all such small isolated colonies, whether of plants or animals, to die slowly out; for they cannot cross freely with any of their own kind outside the narrow limits of their own restricted community; and by constantly breeding in and in with one another they at last acquire such weak and feeble constitutions that they finally dwindle away imperceptibly for want of a healthy infusion of fresh external blood.
Fig. 42. — Lady’s Slipper (Cypripedium calceolius).
If I mention a few other like cases (as well as I can remember them on the spur of the moment, for I cannot pretend to give a complete ex-cathedrâ list here on the slopes of Mynydd Mawr) it will help to elucidate the origin and nature of this little colony of mountain tulips. There is a lovely orchid, the lady’s slipper, common in Siberia and Russia, almost up to the Arctic Circle, but now found with us only in one Yorkshire station, where, like the Perthshire heath, it is rapidly verging to complete local extinction. Again, among one family alone, the tufted saxifrage has now been driven to the summits of Ben Avers and Ben Nevis; the drooping saxifrage is extinct everywhere in Britain save on the cloudy top of Ben Lawers; the brook saxifrage lingers on upon the same mountain, as well as on Ben Nevis and Lochnagar; and the Alpine saxifrage, though more frequent in little solitary groups in Scotland and the Lake district, has died out of all Ireland save only on the bald head of Ben Bulben in Sligo. The Alpine sow-thistle, an Arctic and snowy weed, is now dying out with us on the tops of Lochnagar and the Clova mountains. The black bearberry yet haunts Ben Nevis and a few other Highland peaks. The Alpine butterwort has been driven even from the mountains in Scotland generally, but still drags on a secluded existence in a few very northern bogs of Caithness and Sutherland; in this respect it resembles the northern holy-grass, an Arctic plant, which Robert Dick, the self-taught botanist of Thurso, discovered among the high pastures near his native town. This same grass strangely reappears in New Zealand, whither it has doubtless been carried from Siberia by its seeds accidentally clinging to the feet of some belated bird; but then such a solitary case in itself shows how impossible is the explanation of the numerous Scotch and Welsh Arctic plants as due to mere chance;
for while in north European mountains similar instances can be counted by hundreds, in New Zealand the coincidence is very rare and almost unparalleled.
The snowy gentian, to continue our list, turns up in a good many little Scotch colonies; but the Alpine lychnis, its companion on the mountain pastures of the Bernese Oberland, is only now known in Britain on the summit of Little Kilrannoch, a Forfarshire mountain, and among the crags of Hobcartin Fell in Cumberland. The bog sandwort, everywhere a rare and dying species, has wholly disappeared from these islands except on the sides of the Widdybank Fell in Durham. Its ally the fringed sandwort loiters late on the limestone cliffs of Ben Bulben in Sligo, as well as on one solitary serpentine hill in the island of Unst among the chilly Shetlands. A tiny pea-flower, the Alpine astragalus, has been driven almost everywhere to the snow-line, but still survives in Scotland among the Clova and Braemar mountains. It is on a single spot in the same exposed Clova range, too, that the closely related yellow oxytrope still grows in diminishing numbers; while its ally the Ural oxytrope holds its own manfully over all the dry hills of the Highlands. I could add to these instances many more; but lunch is waiting to be eaten in the knapsack, and I am loth to tire the patience of my hearers with too long a list of barren names and bare wind-swept mountain summits.
Still, I love to think that the little colony of timid shrinking Lloydias stranded here on the granite slopes of Mynydd Mawr can push back its pedigree in such an unbroken line to so dim and distant a prehistoric past. Ever since the glaciers last cleared away from this boss of smooth stone on whose broad back we are sitting, a tiny group of our pretty mountain tulips has continuously occupied age after age this self-same spot. Originally, no doubt, they covered the whole sides of the mountains and stretched down far into the plains and valleys; but gradually, as the world’s weather grew warmer, they were restricted, first, to the mountain tracts of Wales and Scotland, then to a small Snowdonian district, and finally, even within that shrunken realm, to two or three isolated peaks. Occasionally, I suppose, a seed from one of the three existing Welsh colonies may be carried by accident into the territory of the others; but it is in the highest degree improbable that the stock has ever been reinforced for the last fifty thousand years from any purely external body of its congeners in the higher Alps or in the Arctic regions. The dark small men of the neolithic age, the Aryan Celts of the bronze period, the conquering Roman from the south, the Englishman, the Scandinavian, the Norman, all have since come, and most of them have gone again; but the Lloydias still hold precarious possession of their solitary remaining strongholds. An analogy from the animal world will help to bring out the full strangeness of this extraordinary isolation. Mount Washington in New Hampshire is the highest peak among the beautiful tumbled range of the White Mountains. On and near its summit a small community of butterflies belonging to an old Glacial and Arctic species still lingers over a very small area, where it has held its own for the eighty thousand years that have elapsed since the termination of the great ice age. The actual summit of the mountain rises to a height of 6,293 feet; and the butterflies do not range lower than the five thousand feet line — as though they were confined on Snowdon to a district between the Ordnance cairn and the level of the little slumbering tarn of Glasllyn. Again, from Mount Washington to Long’s Peak in Colorado, the distance amounts to 1,800 miles; while from the White Mountains to Hopedale in Labrador, where the same butterflies first reappear, makes a bee-line of fully a thousand miles. In the intervening districts there are no insects of the same species. Hence we must conclude that the few butterflies left behind by the retreating main-guard of their race on that one New Hampshire peak have gone on for thousands and thousands of years, producing eggs and growing from caterpillars into full-fledged insects, without once effecting a cross with the remainder of their congeners among the snows of the Rocky Mountains or in the chilly plains of sub-Arctic America. So far as they themselves know, they are the only representatives of their kind now remaining on the whole earth, left behind like the ark on Ararat amid the helpless ruins of an antediluvian world. Well, what these Mount Washington butterflies are among insects, that are our pretty wild tulips here among English flowers. They remain to us as isolated relics of an order that has long passed away; and they help us to rebuild with fuller certainty the strange half-undeciphered history of the years that were dead and gone long before written books had yet begun to be.
VII. A FAMILY HISTORY.
Fig. 43. — Common Cinquefoil.
Although the roses, like many other highly respectable modern families, cannot claim for themselves any remarkable antiquity — their tribe is only known, with certainty, to date back some three or four millions of years, to the tertiary period of geology — they have yet in many respects one of the most interesting and instructive histories among all the annals of English plants. In a comparatively short space of time they have managed to assume the most varied forms; and their numerous transformations are well attested for us by the great diversity of their existing representatives. Some of them have produced extremely beautiful and showy flowers, as is the case with the cultivated roses of our gardens, as well as with the dog-roses, the sweet-briars, the may, the blackthorn, and the meadow-sweet of our hedges, our copses, and our open fields. Others have developed edible fruits, like the pear, the apple, the apricot, the peach, the nectarine, the cherry, the strawberry, the raspberry, and the plum; while yet others again, which are less serviceable to lordly man, supply the woodland birds or even the village children with blackberries, dewberries, cloudberries, hips, haws, sloes, crab-apples, and rowanberries. Moreover, the various members of the rose family exhibit almost every variety of size and habit, from the creeping silver-weed which covers our roadsides or the tiny alchemilla which peeps out from the crannies of our walls, through the herb-like meadow-sweet, the scrambling briars, the shrubby hawthorn, and the bushy bird-cherry, to the taller and more arborescent forms of the apple-tree, the pear-tree, and the mountain ash. And since modern science teaches us that all these very divergent plants are ultimately descended from a single common ancestor — the primæval progenitor of the entire rose tribe — whence they have gradually branched off in various directions, owing to separately slight modifications of structure and habit, it is clear that the history of the roses must really be one of great interest and significance from the new standpoint of evolution. I propose, therefore, here to examine the origin and development of the existing English roses, with as little technical detail as possible; and I shall refer for the most part only to those common and familiar forms which, like the apple, the strawberry, or the cabbage rose, are already presumably old acquaintances of all my readers.
The method of our inquiry must be a strictly genealogical one. For example, if we ask at the present day whence came our own eatable garden plums, competent botanists will tell us that they are a highly cultivated and carefully selected variety of the common sloe or blackthorn. It is true, the sloe is a small, sour, and almost uneatable fruit, the bush on which it grows is short and trunkless, and its branches are thickly covered with very sharp stout thorns; whereas the cultivated plum is borne upon a shapely spreading tree, with no thorns, and a well-marked trunk, while the fruit itself is much larger, sweeter, and more brightly coloured than the ancestral sloe. But these changes have easily been produced by long tillage and constant selection of the best fruiters through many ages of human agriculture. So, again, if we ask what is the origin of our pretty old-fashioned Scotch roses, the botanists will tell us in like manner that they are double varieties of the wild burnet-rose which grows beside the long tidal lochs of the Scotch Highlands, or clambers over the heathy cliffs of Cumberland and Yorkshire. The wild form of the burnet-rose has only five simple petals, like our own common sweet-briar; but all wild flowers when carefully planted in a rich soil show a tendency to double their petals; and, by selecting for many generations those burnet-roses which showed this doubling tendency in the highest degree, our florists have
at last succeeded in producing the pretty Scotch roses which may still be found (thank Heaven!) in many quiet cottage gardens, though ousted from fashionable society by the Marshal Niels and Gloires de Dijon of modern scientific horticulturists.
Now, if we push our inquiry a step further back, we shall find that this which is true of cultivated plants in their descent from wild parent stocks, is true also of the parent stocks themselves in their descent from an earlier common ancestor. Each of them has been produced by the selective action of nature, which has favoured certain individuals in the struggle for existence, at the expense of others, and has thus finally resulted in the establishment of new species, having peculiar points of advantage of their own, now wholly distinct from the original species whose descendants they are. Looked at in this manner, every family of plants or animals becomes a sort of puzzle for our ingenuity, as we can to some extent reconstruct the family genealogy by noting in what points the various members resemble one another, and in what points they differ among themselves. To discover the relationship of the various English members of the rose tribe to each other — their varying degrees of cousinship or of remoter community of descent — is the object which we set before ourselves in the present paper.
