VII.-Notes on Canadian Polypetala.

By JOHN MACOUN, A.M., F.L.S.

(Read May 22, 1883.)

During the past winter I have been making a particular study of the Canadian Polypetalæ as regards distribution and synonymy, and purpose in the following notes to record a few of the results. Owing to the prominence of the greater number of the species of this section, they have been to a large extent detected and identified, and hence we can consider that less has yet to be done in this direction than in any other.

The following orders, genera, and species have been found within our limits, which are made to include Alaska and Newfoundland as well as every part of the Dominion. They are tabulated and arranged to show the botanical districts into which, for the sake of comparison, I have divided the whole area. The districts are:

I. British Columbia and Alaska northward to the Arctic circle.

II. Rocky Mountains from latitude 49° to the Arctic circle.

III. The region lying east of the Rocky Mountains and extending to the Red River Valley, and including the whole country north to the Arctic circle between James Bay and the Rocky Mountains.

IV. From Red River Valley, or the edge of the forest eastward to Rivière du Loup in Quebec. This area includes all Ontario and much of Quebec.

V. Includes the Atlantic provinces and the eastern part of Quebec, with Labrador and Newfoundland.

VI. All the country north of the Arctic circle.

An analysis of the table (page 152) will show that British Columbia, although least known, has nearly as many species as Ontario and Quebec, but that no less than fifteen of the forty-seven orders are absent. These orders, representing one third of the whole number, contain twenty-three genera, and twenty-eight species. The Ontario and Quebec flora, on the other hand, includes forty-five orders, and the two which are absent contain only two genera and four species. The orders wanting in British Columbia are:

The orders wanting in the Ontario and Quebec flora are:

It is very probable, however, that the former will be detected in Ontario or Quebec as it has been found in Maine.

The Rocky Mountains seem to be the eastern limit of many western species, but present no barrier to the eastern, as nearly all the species that reach the eastern base appear again on the west side. The Coast Range, however, is the true boundary of the eastern species, and many disappear on its eastern slopes. West Coast plants, when found in the interior, are mountain species of which many examples are known amongst the Saxifragaceæ. An examination of mountain and coast species leads me to think that the hygrometric condition of the atmosphere has much to do with the distribution of such species, and that the species comprising the mountain flora generally prefer, if they do not require, an atmosphere almost constantly at the point of saturation. Mountain or northern species seem as much at home in a peat bog in a low latitude as they are in their native habitats, and the cause is not far to seek. Such bogs are cool all summer, and the air over the bog close to the surface is at the dew-point nearly all the time. Southern species, though natives of a swamp, should be looked for on warm sandy tracts, as they there meet with the continuous heat that they seem to require. The one finds in the cold water of the bog compensation for the want of moisture in the air, while the other, imbibing less moisture, seems to need less heat, and both, in their changed condition, live in the same locality, thrive and ripen their seeds year after year.

In studying the present aspect of our flora, one is irresistibly led to look at the past, and although I am not prepared to speak dogmatically of it, yet, with the aid of other workers, I may be able to throw some light on the subject. The problem is one that I approach with diffidence, as many able men have already given their views on the subject, and my investigations may lead me to differ from them. After carefully examining all the available writings on the subject of the origin and dispersal of species, I am strongly impressed with the conviction that our present flora originated at the north, and not it alone but all floras of which we have any record in the rocks. This view was adopted to a certain extent by our esteemed president nearly four years ago, in his able article on "The Genesis and Migrations of Plants." Asa Gray, who, of all living botanists, knows most in regard to the distribution of species on the American continent, in an article written in 1878, says:-"Long genealogies deal more or less in conjecture; but we appear to be within the limits of scientific inference when we announce that our existing temperate trees came from the north, and within the bounds of high probability when we claim not a few of them as the originals of present species." My reasons for adopting this view in a more extended sense I will give in a few words.

1. Darwin in his work on "The Origin of Species," propounds the doctrine of Natural Selection, and in discussing it, seems to state that anything and everything that tends to develop, restrict, weaken or strengthen a species belongs to his theory, and he brings to his assistance another doctrine-the Survival of the Fittest, which I interpret to mean the survival of the strongest, that is, those endowed with the greatest vitality. Now, it is a well understood law that all plants become more prolific as they approach the northern confines of their restricted area, and as they approach their southern limit they produce little else but leaves. Numerous examples could be adduced to establish this from both kingdoms of nature. In the north, therefore, we have vigor and the power of reproduction, while in Sec. IV., 1883. 20

the south, weakness and eventually extinction. Hence a southern dispersion is a destructive one. Species weakened by a southern migration can never return; and, in examining our fossil or living floras, we find that species, when once displaced, never re-occupy the vacated district by a return from the south. When I say weakened, I mean that the species become so changed by heat that it is unable to resist the cold of its old habitat. Examples by the score might be given of plants which have lost their power of resistance to the cold. by being cultivated in a more equable climate.

2. Many years since, Edward Forbes propounded the theory of "Centres of Creation,” and Sir Charles Lyell and Mr. Darwin, both held views that were in accord with Forbes. My view is that our flora originated far to the north-was, in fact, circumpolar—and descended on longitudinal lines to the south before the advancing cold of the glacial epoch. This view harmonizes with the distribution of our own flora, and shows why our eastern species have so little in common with Greenland, while the western shores are largely clothed with Asiatic species, and the Rocky Mountains present no barrier to western extension. The survival of the fittest is well seen in the adaptability of these new arrivals to their changed conditions. Whether we are believers in natural selection or not, we can see a few types, by the operation of these or other laws, becoming an innumerable army, and actually taking possession of the whole land-sweeping the old flora out of existence, or pressing it more to the south, or isolating it, as we believe is the case with the big trees of California. This is clearly shown by the following table.

3. The six leading orders of the Polypetalæ in our flora are:

The whole flora consists of 900 species and 47 orders, yet in these six orders we have no less than 563 species, or nearly three-fifths of the whole. Those which pass beyond the Arctic circle number 230 species, and of these six orders 193, or within 37 of the whole number. In Miocene times only seventeen species of these orders left a record in the rocks, and I note this as one reason why I believe them to be the newer, if not the newest, types of creation.

It is singular that these orders are easily distinguished and stand out from all others by distinctive characters, which plainly separate them from other orders. But within the orders themselves genera and species are unstable, and varietal forms are almost as numerous as species and generic differences, I might say, are at the will of the systematist. Now, here are five types of vegetation which are eminently Arctic, eminently vigorous, and pre-eminently varietal, and are at the present time in our flora fulfilling all the condi

tions of Darwin as regards natural selection, but they are keeping within their own limits.

4. Let us now turn to the past. In Sir Joseph Hooker's "Arctic Manual of Instruction, 1875," at page 380 there is a list of the Miocene plants of the Arctic Regions, by Heer, numbering 353 species of these 88 are Polypetalæ, and only seventeen belong to the orders which are so extensive now. The six most prominent orders of the Miocene

Including the twelve orders mentioned, we have forty-nine species out of a total of eighty-eight, and the genera to which they belong are chiefly represented in our flora. It would seem, therefore, that the small orders are the remnants of vegetation of the past, and that, if there be any links to connect the Magnoliacea and the Ranunculaceae (the Dilleniaceæ are wholly southern) or the Sapindacea with the Leguminosae, we must look to the Pliocene for such connections. The imperfection of the record is certainly a good excuse, but there is a great gap between the Crowfoots and the Magnolias, and, when I look to the tulip-tree which is evidently the older, towering to the heavens and adorned with its clusters of lovely flowers, and to the lowly buttercup at its foot, I am led to ask if this can be a product of natural selection and if plants like men are under a curse.

5. I have stated that I believe our large orders are the newer types and the small ones the older creations. My reasons for these statements are that this variation is apparently still going on in these orders, and many of the species and even genera are difficult to limit. They are chiefly confined to the temperate regions and have few representatives in the tropics. On the other hand the small orders were prominent in the Miocene, they have ceased to vary and are more largely represented in the localities where, if my opinions are correct, both the north temperate and south temperate floras retreat when they are displaced by the vigorous forms originating further to the north or to the south. By this simple law of displacement (for it is a law, which all enforced or voluntary emigrations prove), and the variations consequent on the change of habitat, new races are being consolidated into species, and, as change after change in the physical condition of the earth takes place, these either pass out of existence, or are forced to the south whence they never return. It is a simple matter to acclimatize a northern species at the south, but a serious business to change the constitution of a southern one so as to resist the cold. Hence I infer that a