Page:Popular Science Monthly Volume 30.djvu/617

Rh 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