Popular Science Monthly/Volume 30/March 1887/A Mount Washington Sandwort
|A MOUNT WASHINGTON SANDWORT.|
By GRANT ALLEN.
WE were not fortunate with our plant-hunting on Mount Washington. Perhaps, for want of a local botanist to show us the lurking-places of the rarer species, we did not succeed in finding all of them. But some of the most interesting to a British naturalist could be gathered everywhere without the trouble of seeking. When the little, puffing, oblique locomotive that drags you up from Marshfield to the summit stopped awhile to rest and refresh itself after its steep climb up Jacob's Ladder, we jumped out eagerly upon the surface of the mountain; and there, among the erratic bowlders of the Great Ice Age, I lighted at once upon broad beds of two plants my eyes had never before beheld in the living state—one, a pretty tufted White Mountain sandwort, and the other a beautiful bright golden avens. So thickly did they cover the ground on that high shoulder of the great ridge, that all the passengers were filling their hands with big nosegays to carry away as mementoes of the mountains. The sandwort in particular starred all the crannies among the rifted rocks with its delicate blossoms, and brightened up the otherwise bare and forbidding soil with the mingled green and white of its densely tufted bunches. Arenaria Grœnlandica is its scientific name—a name that tells at once the better part of its curious history; for this little plant belongs by rights to the frozen shores of far northern Greenland, and the little colony that lingers on here in the clefts of the rock has lived on the chilly summits of the "White Mountains ever since the close of the Glacial Epoch.
There are many other flowers on the slopes of Mount Washington far more full of interest to the American botanist than this Greenland sandwort, because far more isolated in the New World, and far more difficult for him to find elsewhere. The sandwort occurs abundantly on several other mountain-summits in the States, being found on the Shawangunks, the Catskills, and the Adirondacks, as well as in the Green Mountains and on the higher peaks round Lake Memphremagog. At Bath, Maine, it even appears on river-banks near the sea, and farther northward, in Labrador and Greenland, it becomes a common plant of the plains and uplands. But the Alpine brook saxifrage (Saxifrage rivularis) confines itself in the States entirely to Mount Washington, as its beautiful congener, the purple saxifrage (S. oppositifolia), does to the rocky crags of Willoughby Mountain in Northern Vermont. So, too, the little creeping mountain potentilla of the Scotch Highlands (Sibbaldia procumbens) is only found in the United States on the Presidential Range of the White Mountains. There are many of these Alpine or sub-Alpine plants which the American botanist can pick here, and here only, unless he chooses to wend his way to the frozen shores of the far North in chilly Labrador and the Hudson Bay Territory. Yet, to the English naturalist, they are comparatively uninteresting, for they form part of the common European mountain flora, which reappears on all the higher peaks of his own continent, from the Alps and the Caucasus to the Norwegian fields and the Scotch Highlands. To him, then, these two native American upland plants present far more numerous points of interest, because this is the only place in the civilized world where he can hope to find them ready to his hand, as representatives of the truly northern New-World flora.
The general aspect of vegetation on the higher levels of the White Mountains, indeed, is distinctly subarctic, or, to give its truer name, as I prefer to say, glacial. Besides the common sun-dews and the grass of Parnassus, which always follow the upland bogs of northern climates on both sides the Atlantic, Mount Washington and his neighbors possess a large number of chilly plants, like the Norwegian cloud-berry (Rubus chamœmorus), the Alpine willow-herb (Epilobium Alpinum), the dwarf rattlesnake-root (Nabalus nanus), the mountain cudweed (Gnaphalium supinum), the bog bilberry (Vaccinium uliginosum), the Alpine bearberry (Arctostaphylos Alpina), and the Lapland phlox (Diapensia Lapponica). Some of these, and others like them, were old friends already familiar to me on European mountains; but some were fresh American acquaintances, whose faces I was glad indeed to see on these bald summits. Both types, however, were alike in their thoroughly northern and almost arctic aspect; they were the plants of Greenland, of Finland, of the North Cape in Norway, of frozen Rupert's Land, of equally frozen Siberia. Some of them were common to both hemispheres, some were peculiar to the New World, but all, indiscriminately, were members of that same old circumpolar flora which came into being at the extreme end of the Pliocene period, when the world was just beginning to cool down at its extremities for the long secular winter of the Glacial Epoch.
Traces of that gradual cooling down are by no means wanting in the geological deposits of either hemisphere. The Pliocene period, as a whole, both in Europe and America, was an age of warm and genial climates, of large and vigorous animal types, of rich, sub-tropical-looking vegetation. In the Red and Norwich crags of England, for example, we find the remains of mastodons and elephants, of hipparions and hyenas, of the hippopotamus and the rhinoceros, of the tapir and the horse. In the rich leaf-beds of the nearly contemporary Vienna basin, we meet with a correspondingly warm sub-tropical flora—a vegetation abounding in sequoias, liquidambars, and chestnuts, fragrant with cinnamon, laurel, and tamarind. In the Loup River beds of the upper Missouri region, again (Professor Marsh's "Niobrara group"), America possesses similar mammalian remains of tropical and almost Oriental character—a tiger larger than the Bengal beast, an elephant, a mastodon, several rhinoceroses, and the earlier sketchy prototypes of the camels and the horses. The period when such warm-weather creatures flourished in such northern latitudes must surely have been one of very genial climatic conditions. But, toward the close of the Pliocene age, mutterings and forewarnings of the great glaciation begin to show themselves, and to herald the advent of that vast ice-sheet which gradually swallowed up in its devouring bosom the better portion of either continent.
Already in the Norwich crag of England the evolution of such northern molluscan species as Scalaria Grœnlandica, Panopœa Norwegica, and Astarte borealis (whose very names attest their arctic habits in our own day), gave evidence of a slow but certain lowering of the world's temperature. Nature only produces these cold-weather types where the surrounding conditions have rendered the change absolutely necessary. In the somewhat later Chillesford beds, the great invasion of arctic kinds begins in earnest; about two thirds of the shells whose fossil remains form the fauna of the period still survive in high northern waters. Slowly, as the period of greatest eccentricity drew nigh, the ice-cap began to form around the north pole. From the Arctic Ocean, the great sheet of solid glacier descended over Canada and the Eastern States till all New England, New York, and Pennsylvania lay covered with five thousand feet thickness of unbroken crystal. The ice cleared all animal and vegetable life off the face of the earth wherever it rested, and drove before it the old arctic fauna and flora as far south as Maryland, Virginia, and Kentucky. After many minor chances and changes, however, brought about by the recurrent cycles of summer and winter in the northern and southern hemisphere alternately, the world's weather began slowly to improve again. Step by step the ice retreated northward once more, till at last only the comparatively insignificant polar cap remained to bear witness to its sway, with a few casual southern extensions, like the one that still envelops all upper Greenland in its desolating sheet. As it slowly retired, the arctic fauna and flora followed close in its rear, on both sides of the Atlantic, till nowadays the plants and animals which once covered the plains of Europe, Canada, and New England find their last home in Spitzbergen, Nova Zembla, and the extreme northern shores of British America.
They left behind, however, some tokens of their presence to the present day even in the lower latitudes of Europe and America. The Greenland sandwort, among the New Hampshire hills, is just as much a relic of the Glacial Epoch as the striated rocks, the erratic bowlders, and the coarse drift which the Great Ice Age stranded high up the slopes and corries of Mount Washington, where we still find them in our own times. All the other glacial species (including that rare White Mountain butterfly which occurs on the very summit of that one peak, and nowhere else south of Labrador) have struggled on side by side with it, in isolated colonies, from the days when the ice retreated northward to the present moment. But there is a great difference in this respect between Europe and America, as Dr. Asa Gray has well pointed out. With us, in the Old World, great lateral ranges of mountain—Alps, Pyrenees, Dovrefjeld, and Caucasus—still nourish large existing glaciers and snow-fields, the lineal descendants of the universal ice-sheet of the Glacial Epoch. Hence, our European mountain flora, and, to a less extent, our mountain fauna as well, are even now large and flourishing; they retain a marked arctic appearance, and recall all the well-known stunted features of the glacial assemblage of plants and animals. The snowy mountain regions have acted as continuous nurseries for the dwarfed vegetation of the Great Ice Age. In America, on the other hand, you have few hills of any size east of that great backbone of the continent, the Rockies, and none of these hills rise to anything like snow-level. Hence, your mountain flora is, on the whole, but a poor one, and most of the species are the familiar kind which the European botanist already knows well among the Swiss Alps and the Scotch Highlands.
Mount Washington, indeed, though the highest of all your North-eastern peaks, is not by any means the best station in the States for the plants of this old stranded glacier stratum. As you go from New York to Montreal by the Memphremagog route, you pass near St. Johnsbury a little station named West Burke, whence stages carry you in a few miles to Willoughby Lake, one of the loveliest among all the lovely sheets of water with which Northern Vermont is so copiously dotted. The hills surrounding Willoughby Lake are rich in mementoes of the Glacial Epoch. There, alone in the States, thanks to combined latitude and elevation, the American botanist can pick at leisure the beautiful tufted mountain saxifrage that purples with its bloom the Highlands of Scotland in early spring. There, too, grows its pretty yellow congener (Saxifrage aizoides), a circumpolar species of both hemispheres, which descends in Europe as far south as the Cambrian lakes. The Alpine rock-cress, the hoary whitlow-grass, the purple astragalus, and many other high northern species, are also almost confined in the States to Willoughby Mountain, though reappearing far to the north in British territory—either Canada or Newfoundland. Mount Katahdin, in Maine, ranks next as a refuge for many good glacial species, including the beautiful little starry saxifrage (Saxifrage stellaris), whose slender blossoms spread in countless numbers beside the rills and streams of the Scotch Highlands.
Naturally, however, to a European visitor, such a plant as the Greenland sandwort possesses a far deeper interest and importance than these old friends of the Swiss or Scotch uplands. It is a native American, local to the soil; or, to speak more correctly, a rare example of a glacial plant which has died out in distant Europe in spite of the superior advantages there afforded to Alpine or sub-arctic species, while it has lingered on in vigorous colonies over all the fitting districts of America, from the riks of Greenland to the Catskills of New York. Nay, more, in a slightly altered and adapted form, as the Arenaria glabra of the systematic botanists, it has held its own even as far south as the mountain-tops of Carolina—a glacial strayling stranded almost alone on the chilliest summits of a sub-tropical land. The Carolina type, as might naturally be expected, is a larger, handsomer, and more luxuriant plant than the New Hampshire and Greenland variety, but it does not differ in any point of real structural or systematic importance from its pretty little sisters of more frozen climes.
Very much the same thing is true of our other common Mount Washington flower, the yellow avens that grows so abundantly in and out among the thick-set beds of Greenland sandwort. This, too, is a thorough-going native American type, though not a type of glacial antecedents. What gave it its deepest interest in our eyes was the very fact that, growing as it did side by side with those sub-arctic plants, the bog-bilberry and the mountain saxifrage, the Alpine bearberry and the Lapland phlox, it yet exemplified the other main element of the American upland vegetation—an element intrusive from the southern mountains rather than from the circumpolar and northern plains. For the avens is, in fact, a New England mountain variation on a pretty plant which covers the higher Carolina hills—Geum radiatum of Michaux, a hairier representative of the self-same type. The more northern outlier, known as the variety Pechii of Pursh, has smoother leaves and somewhat glabrous stems, but otherwise keeps up the general characteristics of its Southern congeners. Just so, on the slides above the Notch of the White Mountains, not far from the Willey House, I found in profusion another essentially Southern plant—the Paronychia argyrocoma, a silvery looking whitlow-wort, whose inconspicuous blossoms, allied to those of our European knarvel, are yet rendered beautiful and noticeable to mountain insects by their numerous thin and shining scarious bracts. This curious plant, one of the most suggestive I found in America, is not known to occur anywhere else in the far Northern States save in this one deep and secluded valley. But, among the Alleghanies, it occupies every breezy summit from Virginia southward, so that it belongs, like the Mount Washington avens, to the sub-tropical mountain flora, and only makes its appearance, as if by accident, among the glacial vegetation of the New Hampshire hills.
How did these isolated Southern species come to obtain a footing in such bleak situations near the northern limit of the United States? Doubtless, in the first instance, their introduction was due to the agency of casual birds, who must have brought the seeds with them, clinging to their feet or legs, on their annual migration from their winter dwelling-places. Once fairly started on the New Hampshire mountains, they succeeded well because naturally adapted to their new situation, where the summer heat would not be far inferior to that of their native Carolinian heights, while the snow-sheet of winter would amply protect them from the killing effects of December frosts.
And this brings us back once more to the point from which we started—the history of our little Mount Washington sandwort. Nothing was more noticeable, as we mounted the slopes on the cog-wheel railway, than the wide sheets of conspicuous blossom that greeted us everywhere with their striking mass. First of all, it was Canadian cornel in broad patches that whitened the soil; then it was great areas of the Greenland sandwort; and then golden spaces of the yellow avens. Now, all the world over, mountain-plants, especially those that grow beyond the limit of trees, and close up to the very snowline, are celebrated for their exceptional display of vivid color. Everybody must at least have heard of the Alpine gentians, globe-flowers, and daffodils, that belt with blue or gold or primrose whole zones of mountain-side in Swiss spring-time. Exactly the same thing is true of the arctic flowers; short as is their summer, they make it beautiful while it lasts, with their profuse bloom, a hundred times more vivid and pervasive than anything to be seen in those much overpraised and misrepresented tropics. Even in temperate Europe and America, everybody must have noticed that, as we go up the higher hills, we find their slopes purpled with heather or golden with gorse, pink with mountain-laurel, or crimson with masses of the wild rhododendron.
Why is this? Simply because among the uplands and more especially close to the snow-line, bees are rare, and the work of fertilization is mainly left to the care of butterflies. Now, the bee, as everybody knows, is a steady, regular, business-like worker: he flies low, hunts close, never mixes his liquors, sticks steadily to one kind of honey produced by one species on each journey, and looks carefully for his selected blossom in and out among the tangled vegetation of meadow or road-side. Hence the flowers that specially cater for his peculiar tastes are more remarkable for their exact adaptation to his size and shape than for any conspicuous floral display. But the butterfly, on the other hand, is well known to be a fickle, flitting, fantastic creature: he flies high from bunch to bunch of large and noticeable bright-hued flowers. Above all other members of the insect tribe, he is a lover of color: big patches of red or white or purple are the things to attract him from a distance with their massive glare, and to draw him down from his careless flight in the eye of heaven. Hence butterfly flowers generally grow in huge trusses, massed closely together to re-enforce one another's effect; and they produce the finest total displays of any species known to humanity. On the hill-tops, and especially close above the limit of trees, the high-flying butterflies have things all their own way. The plants that affect these chilly situations, therefore, have before been compelled to accommodate themselves to the circumstances, and to trust for fertilization to the stray attentions of the casual butterfly. It is not without reason, then, that on the summit of Mount Washington a specialized and peculiar glacial butterfly should still accompany the specialized and peculiar glacial flowers.
Our Greenland sandwort, indeed, may be taken as a very good representative of the qualities necessary for ultimate success in a high-mountain plant. It grows low, in densely tufted masses, unlike the majority of its family, the Alsinœ; and thus it escapes both the rapid winds that career so madly round the summits of the Presidential Range, and the frosts of winter from which the snow efficiently protects its humble branches. Its blossoms rise in immense numbers from every tuft, so as to whiten the ground wherever it grows; and the petals are immense for the size of the plant, to act as an advertisement to the passing butterfly. Turn from it for a moment to the beautiful moss-campion (Silene acaulis) which grows close by among the crannies of the Mount Washington rocks, and you get a precisely similar assemblage of mountain features. That dainty little plant is tufted like a moss; its leaves are as crowded as those of the sandwort, and similar in shape, for like conditions always produce like results; and its purple blossoms grow in exactly the same wild profusion, making the whole plant, during the flowering season, into one low mat of brilliant bloom. The moss-campion is a perennial, and its close habit and much-branched, creeping stem protect it from the severe winter of New Hampshire, as from the Scotch snows and the frosts of Switzerland. We have in Europe another precisely similar plant, the Alpine lychnis, which one might almost at first sight confuse at a distance with the moss-campion, so absolutely have they accommodated themselves in the same way to the same environment; and this pretty pink flower, with its compactly clustered heads, has survived only on two hill-tops in the British Isles—Little Kilrannoch, a mountain in Forfarshire, and Hobcartin Fell, one of the least visited of our Cambrian heights. Compare the case of the glacial American species which still loiter round Willoughby Lake, or on the frozen heights of Mount Katahdin in Maine.
Every one of these mountain-plants exhibits in perfection the self-same familiar mountain characteristics. Take, for example, the white dryas (Dryas octopetala), a species of interest to American botanists from the fact that in Pursli's time it still grew among the White Mountains, though it has now disappeared entirely from the Ignited States, and can not be discovered south of Lower Canada. (Such local disappearances, by-the-way, are everywhere common, more than one rare local plant having been expunged from the British flora within my own memory.) The dryas is a dwarf and matted perennial herb or undershrub, growing in tufts just like the moss-campion, and with starry white flowers to match the Greenland sandwort. Its short and much-branched stems creep close upon the ground; the prostrate branches are crowded with dense foliage in spreading tufts. The species, in fact, with the rest of its kind, is but a specialized mountain form of avens; and its flowers are white, not yellow, like most of the avens group, in special adaptation to the butterfly taste; for it is a noteworthy fact that many genera which are yellow in the lowlands tend to produce white and purple species when they rise among the mountains or near the Arctic Circle.
The moss-campion is a pink by family, while the dryas is a rose. Now look once more at a member of a totally distinct order, the Lapland phlox, which also grows among the ice-worn bowlders of the Presidential Range. The phloxes as a whole are tall and handsome, large-leaved plants; but the mountain kind (Diapensia Lapponica), that still lingers on among the New Hampshire heights and the higher Adirondacks, is an Alpine dwarf evergreen, growing in the regulation dense convex tufts, a perfect mat of intricated leaves, from whose little rosettes rise solitary large white blossoms, as handsome as the dryas, and not unlike it in general effect. Anybody who cultivates rock-gardening, indeed, must be thoroughly familiar with this curious mat-like habit of the northern mountain flora; for many of the saxifrages, alyssums, arenaries, and stone-crops which form his favorite masses of bloom are members of this truly Alpine and sub-Arctic vegetation. Often their very names betray their origin: lovers of rock-gardens will know what I mean when I mention such cases as Erinus Alpinus, Lychnis Lapponica, Sedum Kamschaticum, Alyssum montanum, Silene alpestris, Dianthus petrœus, Saxifrage nivalis, and Arenaria montana.
Nor is it only herbaceous species that undergo this curious dwarfing and acquire this strange matted tuftiness, in order to meet the needs of high Arctic and Alpine situations. Trees and bushes have similarly to accommodate themselves to the exceptional conditions of the snowline and the region just below it. Every tourist who goes up Mount Washington must have noticed how, near the limit of arboreal vegetation, the pines and spruces grow shorter and more stunted by slow degrees, till at last they disappear altogether from the scene. But even after they are gone, so far as the naked eye is concerned, they persist in part for the eye of the botanist. Three dwarf willows, for example, occupy the summits of the White Mountains, beyond the so-called limit of trees. All of them are prostrate, matted, and Alpine in type; none of them rises above the general level of the herbaceous vegetation in whose midst they are found. The first, known as Cutter's willow, may also be gathered among the other higher mountains of the extreme Northern States, such as the Adirondacks and the Maine ranges. The second, the silvery-pointed willow, a very pretty plant of glossy, satin-like sheen when young, is confined to the moist Alpine ravines of the White Mountains themselves. The third and most dwarfish species of all, the herbaceous willow, has lost all resemblance of its descent from what was once a forest tree, and has degenerated into a rare ordinary herb, seldom rising above an inch or two from the ground, but still producing from its terminal buds the tiny catkins which keep up the memory of its former high estate. This last degraded scion of the willow stock, which creeps and roots underground for considerable distances, is common to both sides of the Atlantic, being found also in the Alps and Pyrenees, as well as in Arctic and sub-Arctic Europe: but the White Mountains are its only known station in the United States.
It is interesting to note that just the same dwarfing of the trees and shrubs took place everywhere during the fiercest rigor of the Glacial Epoch. In the little bed of glacial clay, containing plant remains of the Great Ice Age, on the coast of Norfolk in England, we still find the leaves of a tiny, shrubby birch (Betula nana), which grows even now in the Highlands of Scotland and in Scandinavia, attaining there at times to tree-like size, but which dwindles near the Arctic Circle to a mere dwarf; and it is the dwarf form whose leaves occur among the glacial débris of the Norfolk clay-bed. Side by side with it we find the scanty remains of a stunted northern willow (Salix polaris), another of the numerous pygmy shapes which the polymorphous willow type knows so well how to take on under fitting circumstances. It is hard, indeed, to conceive how anybody could ever have watched the gradual stunting of the trees and shrubs, as we ascend a mountain, or approach the Arctic Circle, and yet believe in the separate and deliberate creation of dwarf forms for such great altitudes or high latitudes, like the Mount Washington willows or the polar birch. If we trace the gradual degeneracy of the temperate birchen type, represented by the beautiful American silver or paper birches, through your own shrubby Betula purinla of the Northern bogs, and your petty Betula glandulosa of the high mountains, to the insignificant Betula nana of the arctic regions and of glacial times, it is impossible not to recognize in the entire series one long degradation of a primitive form. Similarly in the willows: every intermediate step may easily be identified, from the large and handsome weeping-willows, through shrubby forms like Salix Lapponum, Salix refens, and Salix myrsinites, till we reach at last the final term in the tiny Salix herbacea of the White Mountains. All are species degraded from a tall and vigorous ancestral tree by the harsh conditions which prevailed at the coming in of the Glacial Epoch.
The shrubs, of course, have fared no better than the forest-trees; but, like the forest-trees themselves, and the lowly herbs, they have learned to accommodate themselves to the situation. Thus the bramble kind, after growing down from the high blackberry and the black raspberry to the level of the trailing dewberry (Rubus Canadensis) and the dwarf raspberry (Rubus trifloms), reaches at last an almost herbaceous type in our British Rubus saxatilis, and finally ends in a mere herb, no bigger than a strawberry-vine, in the true cloudberry of the arctic regions and the New Hampshire hills. So, too, the cornels, starting with your glorious flowering dogwood (Cornus florida), which alone is worth a visit across the Atlantic to see, ends at last in the pretty little bunchberry (C.canadensis) that carpets the woodlands of the high North. And so, once more, the heath family, starting from the noble rhododendron and mountain laurels that glorify and brighten your American hills, tails off at last into the low, spreading, and tufted bog-bilberry, confined entirely to Alpine tops on both sides of the water, and to the mountain bearberry, whose low mats cover the interstices of the rocks among the White Mountains and the higher Maine hills. Everywhere the habit of all these sub-Arctic and glacial plants is just the same, whether their ancestors started in life as trees, or shrubs, or bushes, or herbs; the Alpine azalea is as low and as tufted as the crowberry that mimics it; the Labrador tea is as tiny and as inconspicuous as the Greenland sandwort. On all of them has fallen the blight of a terrible winter, never yet removed; and all struggle on among the chilly mountains and the northern snow-fields in virtue of that very constitution and character which they derived from their ancestors of the Glacial Age.