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Page:Popular Science Monthly Volume 32.djvu/202

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THE POPULAR SCIENCE MONTHLY.

weed, and herbaceous annuals were doubtless the earliest form of all vegetation all the world over. Once more, the leaves are divided into three leaflets; and this type I take from its frequent recurrence not only among the potentillas themselves, but in the strawberries, the lady's-mantle, the simpler brambles, and many other species as well, to have been the original type of foliage for the entire rose family. Finally, certain minute technical characters in the stipules and the styles, with which I need not trouble you at the present moment, lead to the conviction that we have here to deal to some extent with a fair representative of the old ancestral potentilla form.

The Norway potentilla, however, is distinctly weedy—that is to say, it is one of those unpleasant, dusty-looking plants which loiter about on the precincts of the road-sides and in the waste purlieus of human cultivation. It attests its weediness by its bristly hairs, intended doubtless to repel insects and to make it unpalatable to cattle and horses. As its name implies, it is an Old-World form as well as a native-born American citizen; it is, in fact, a member of that ancient circumpolar pre-glacial flora which was driven down from the once mild and genial Arctic regions by the vast ice-sheet of the Glacial epoch to occupy the plain-lands of either hemisphere in these our chilly and degenerate modern summers. In Europe, however, it remains distinctly a more northern type than with you in America, where it spreads as far south as the Virginia hills.

On the Alpine tops of the White Mountains I was lucky enough to light upon another member of the potentilla group, not far removed in essentials from the Norwegian weed, but infinitely prettier, more delicate, and in a word less weedy all round. This is the plant which Asa Gray identifies with our European Potentilla frigida of the Swiss Alps; and I, who have a pious horror of unnecessary splitting and renaming and tinkering, have not the slightest objection to the identification in any way. But it is worth while to notice, what I often observed of almost every American species said to be identical with those of Europe, that the two plants are not absolutely the same: the time that has elapsed since the Great Ice age effectually severed the two continents has sufficed to produce distinct differences in nearly every kind of plant or animal. The flowers in the American specimens are smaller than in the Swiss, and the stems when full-grown are far less hairy.

Potentilla frigida exhibits all the common peculiarities of high Alpine or Arctic plants. It is a dwarf form, not one fifth the size of the Norway species; it is tufted thickly on its low stems, and it has that matted, close, creeping habit which I have already pointed out in this "Monthly" as the distinctive feature of the glacial flora. It sticks still to the three original leaflets, but its flowers, as is common in mountain types, are far larger and handsomer than those of the wayside weed with which we started our examination of the group. This Old-World