Another plant which, being less dependent on shade and shelter than the Linnæa, mounts still higher, is the cowberry or foxberry (Vaccinium vitis-Idæa). This, also, is both European and American, and is probably a survivor of the Pleistocene period. It still occurs in at least one locality in the low country of Massachusetts, and on the coast of Maine. It is found along the granitic coast of Nova Scotia, and extends thence northward to the Arctic circle, being found at Great Bear Lake and at Unalaska. This, too, is a most unchanging species, and the same statement may be made respecting the cloudberry (Rubus Chamæmorus), the black crowberry (Empetrum nigrum), the Labrador tea (Ledum latifolium), the three-toothed cinquefoil (Potentilla tridentata), which grows on the coast of Nova Scotia, and is found in the nodules of the Ottawa clay, the same in every detail as on Mount Washington, the bog bilberry (Vaccinium uliginosum), and the dwarf bilberry (V. cæspitosum). Several of these, too, it will be observed, are berry-bearing plants, whose seeds must be deposited in all kinds of localities by birds. Yet they never occur in the warm plains, nor do they show much tendency to vary in the distant and somewhat dissimilar places in which they occur. In the case of most of these species, the most careful comparison of specimens from Mount Washington with those from Labrador, shows no tittle of difference. When we consider the vast length of time during which such species have existed, and the multiplied vicissitudes through which they have passed, one is tempted to believe that it is the tendency of the "struggle for existence" to confirm and render permanent the characters of species rather than to modify them.
Of the more specially Arctic plants which have held their ground unchanged on Mount Washington, the following are some of the principal. Diapensia Lapponica, in beautiful deep green tufts, ascends quite to the summit. It occurs also in the Adirondack Mountains, on Mount Katahdin, in Maine, and on the summit of Mount Albert, Gaspé (Macoun). It is found in Labrador, and, according to Hooker, extends north to Whale Island, in the Arctic seas; but it is not found west of the Great Fish River. It occurs also on the mountains of Lapland, and is described as the hardiest plant of that bleak region. Arenaria (Alsine) Grænlandica, the Greenland sand-wort, adorns with its clusters of white flowers every sandy crevice in the rocks of the very summit of Mount Washington, and is trodden under foot like grass by the hundreds of careless sightseers that haunt that peak in summer; though I should add, that not a few of them carry off little tufts as a memento of the mountains, along with the fragments of mica which appear to form the ordinary keepsakes of unscientific visitors. It is a most frail and delicate plant, seemingly altogether unsuited to the dangerous pre-eminence which it seeks, yet it loves the bare, unsheltered mountain peaks, and when it occurs in the more sheltered ravines, has only its stems a little longer and more slender. It occurs on the Adirondack Mountains and on Katahdin, where, if I may judge from specimens kindly sent to me by Prof. Goodale, it attains to smaller dimensions than on Mount Washington, on the Catskills, and at one place on the sea coast of Maine. I have not seen it in Nova Scotia, but it ranges north to Greenland.
Another of the truly Arctic plants is the alpine azalea (Loiseleuria procumbens), a densely tufted mountain shrub, with hard glossy leaves, that look as if constructed to brave extremest hardships. It is found on the mountains of Norway, at the height of 3,550 feet on the Scottish hills, according to Watson, and according to Fuchs, at the height of 7,000 feet in the milder climate of the Venetian Alps. In America it is found in Newfoundland, in Labrador, at 4,000 feet on Mount Albert, Gaspé,[199] and in the barren grounds from lat. 65 to the extreme Arctic islands. Gray does not mention its occurrence elsewhere in the United States than the summits of the White Mountains. A member of the same family of the heaths, the yew-leaved phyllodoce (P. taxifolia), presents a still more singular distribution. It is found on all the higher mountains of New England and New York, and occurs also on the mountains of Scotland and Scandinavia, but its only known station in northern America is, according to Hooker, in Labrador. As many as nine or ten of the Alpine plants of the White Mountains belong to the order of the Heaths (Ericaceæ). Another example from this order is Rhododendron Lapponicum, a northern European species, as its name indicates, and scattered over all the high mountains of New England and New York, occurring also in Labrador, on the Arctic sea coasts, and the northern part of the Rocky Mountains, and at 4,000 feet on Mount Albert, Gaspé (Macoun).
[199] Macoun.
It would be tedious to refer in detail to more of these plants, but I must notice two herbaceous species belonging to different families, but resembling each other in size and habit the Alpine epilobium (E. alpinum or alsinefolium), and the Alpine speedwell (Veronica alpina). Both are in the United States confined to the highest mountain tops. Both occur as alpine northern plants in Europe, being found on the Alps, on the Scottish Highlands, and in Scandinavia. Both are found in Labrador and on the Rocky Mountains, and the Veronica extends as far as Greenland. The Alpine epilobium is one of the few White Mountain plants that have attained the bad eminence of being regarded as doubtful species. Gray notes as the typical form, that with obtuse and nearly entire leaves, and as a variety, that with acute and slightly toothed leaves, which some other botanists seem to regard as distinct specifically. Thus we find that this little plant has been induced to assume a suspicious degree of variability; yet it is strange that both species or varieties are found growing together, as if the little peculiarities in the form of the leaves were matters of indifference, and not induced by any dire necessities in the struggle for life. Facts of this kind are curious, and not easily explained under the supposition either of specific unity or diversity. For why should this plant vary without necessity? and why should two species so much alike be created for the same locality? Perhaps these two species or varieties, wandering from far distant points of origin, have met here fortuitously, while the lines of migration have been cut off by geological changes; and yet the points of difference are too constant to be removed, even after the reason for them has disappeared. If this could be proved, it would afford a strong reason for believing the existence of a real specific diversity in these plants.
I have said nothing of the grasses and sedges of these mountains; but one of them deserves a special notice. It is the Alpine herd's grass (Phleum alpinum), a humble relation of our common herd's grass. This plant not only occurs on the White Mountains, in Arctic America, in the Canadian Mountains, from the summit of Mount Albert, in Gaspé, to the mountains of British Columbia, and on the hills of Scotland and Scandinavia, but has been found on the Mexican Cordillera and at the Straits of Magellan. The seeds of this grass may perhaps be specially suited for transportation by water, as well as by land. It is observed in Nova Scotia that when the wide flats of mud deposited by the tides of the Bay of Fundy, are dyked in from the sea, they soon become covered with grasses and carices, the seeds of which are supposed to be washed down by streams and mingled with the marine silt; and fragments of grasses abound in the Post-tertiary clays of the Ottawa.
It seems almost ridiculous thus to connect the persistence of the form of a little plant with the subsidence and elevation of whole continents, and the lapse of enormous periods of time. Yet the Power which preserves unchanged from generation to generation the humblest animal or plant, is the same with that which causes the permanence of the great laws of physical nature, and the continued revolutions of the earth and all its companion spheres. A little leaf, entombed ages on ages ago in the Pleistocene clays of Canada, preserves in all its minutest features the precise type of that of the same species as it now lives, after all the prodigious geological changes that have intervened. An Arctic and Alpine plant that has survived all these changes maintains, in its now isolated and far removed stations, all its specific characters unchanged. The flora of a mountain top is precisely what it must have been when it was an island in the glacial seas. These facts relate not to hard crystalline rocks that remain unaltered from age to age, but to little delicate organisms that have many thousands of times died and been renewed in the lapse of time. They show us that what we call a species represents a decision of the unchanging creative will, and that the group of qualities which constitutes our idea of the species goes on from generation to generation animating new organisms constructed out of different particles of matter. The individual dies, but the species lives, and will live until the Power that has decreed its creation shall have decreed its extinction; or until, in the slow process of physical change depending on another section of His laws, it shall have been excluded from the possibility of existence anywhere on the surface of the earth, unless we suppose with modern evolutionists that there is a possibility of these plants so changing their characters that in the lapse of ages they might appear to us to be distinct specific types. The fact, however, that the Arctic species have migrated around the whole Arctic circle, and have advanced southward and retreated to the north, again and again, without changing their constitutions or forms, augurs for them at least a remarkable fixity as well as continuity.
While the huge ribs of mother earth that project into mountain summits, and the grand and majestic movement of the creative processes by which they have been formed, speak to us of the majesty of Him to whom the sea belongs, and whose hand formed the dry land, the continuance of these little plants preaches the same lessons of humble faith in the Divine promises and laws, which our Lord drew from the lilies of the field.
It is suggestive, in connection with the antiquity and migrations of these plants, to consider the differences in this respect of some closely allied species of the same genera. Of the blueberries that grow on the White Mountains, one species, Vaccinium uliginosum, is found in Behring's Straits and very widely in Arctic and boreal America,[200] also in northern Europe. V. cæspitosum has a wide northern range in America, but is not European. V. Pennsylvanicum and V. Canadense, from their geographical distribution, do not seem to belong to the Arctic flora at all, but to be of more southern origin. The two bearberries (Arctostaphylos uva-ursi and alpina) occur together on the White Hills, and on the Scottish and Scandinavian mountains; but the former is a plant of much wider and more southern distribution in America than the latter. Two of the dwarf willows of the White Mountains (Salix repens and S. herbacea) are European as well as American, but S. uva-ursi seems to be confined to America. Rubus triflorus, the dwarf raspberry, and R. chamæmorus, the cloud berry, climb about equally high on Mount Washington; but the former is exclusively American, and ranges pretty far southward, while the latter extends no farther south than the northern coast of Maine, and is distributed all around the Arctic regions of the Old and New Worlds. It is to be observed, however, that the former can thrive on rich and calcareous soils, while the latter loves those that are barren and granitic; but it is nevertheless probable that R. triflorus belongs to a later and more local flora. Similar reasons would induce the belief that the American dwarf cornel or pigeon-berry (Cornus Canadensis), whose distribution is solely American, and not properly Arctic, is of later origin than the C. Suecica,[201] which occurs in northern America locally, and is extensively distributed in northern Europe.
[200] Macoun, Catalogue of Canadian plants.