Outlines of the Distribution of Arctic Plants

Part One (J.D. Hooker)

Editor’s note: This important essay first appeared in the Transactions of the Linnean Society of London, vol. 23 (1862), pp. 251–348. Part One is a transcription of pp. 251–261 of the original; additional material will be added as and when I get time. The original footnotes are shown [in brackets]. Any hyperlinks in the text will take you to other information on this site about the person, etc referred to: use your browser’s "Back" button to return to this page.

[Contents: not included in original article.]

• On the Local Distribution of Plants within the Arctic Circle
• On the Distribution of Arctic Flowering Plants in various Regions of the Globe
• Common to Arctic Europe and Temperate Asia, &c., but not to Alps of Europe

XVII. Outlines of the Distribution of Arctic Plants.
By Jos. D. Hooker, M.D., F.R.S., &c.
(With a Map. Plate XXXII.)

Read June 21st, 1860.

I SHALL endeavour in the following pages to comply, as far as I can, with a desire expressed by several distinguished Arctic voyagers, that I should draw up an account of the affinities and distribution of the flowering plants of the North Polar Regions. The method I have followed has been, first to ascertain the names and localities of all plants which appear on good evidence to have been found north of the arctic circle in each continent; then to divide the polar zone longitudinally into areas characterized by differences in their vegetation; then to trace the distribution of the arctic plants, and of their varieties and very closely allied forms, into the temperate and alpine regions of both hemispheres. Having tabulated these data, I have endeavoured to show how far their present distribution may be accounted for by slow changes of climate during and since the glacial period.

The arctic flora forms a circumpolar belt of 10° to 14° latitude, north of the arctic circle. There is no abrupt break or change in the vegetation anywhere along this belt, except in the meridian of Baffin’s Bay, whose opposite shores present a sudden change from an almost purely European flora on its east coast, to one with a large admixture of American plants on its west.

The number of flowering plants which have been collected within the arctic circle is 762 (Monocot. 214; Dicot. 548). In the present state of cryptogamic botany it is impossible to estimate accurately the number of flowerless plants found within the same area, or to define their geographical limits; but the following figures give the lest approximate idea I have obtained:

Regarded as a whole, the arctic flora is decidedly Scandinavian; for Arctic Scandinavia, or Lapland, though a very small tract of land, contains by far the richest arctic flora, amounting to three-fourths of the whole; moreover upwards of three-fifths of the species, and almost all the genera, of Arctic Asia and America are likewise Lapponian, leaving far too small a percentage of other forms to admit of the Arctic Asiatic and American floras being ranked as any-thing more than subdivisions, which I shall here call districts, of one general arctic flora.

Proceeding eastwards from Baffin’s Bay, there is, first, the Greenland district, whose flora is almost exclusively Lapponian, having an extremely slight admixture of American or Asiatic types : this forms the western boundary of the purely European flora. Secondly, the Arctic European district, extending eastward to the Obi river, beyond the Ural range, including Nova Zembla and Spitzbergen; Greenland would also be included in it, were it not for its large area and geographical position. Thirdly, the transition from the comparatively rich European district to the extremely poor Asiatic one is very gradual; as is that from the Asiatic to the richer fourth or West American district, which extends from Behring’s Straits to the Mackenzie River. Fifthly, the transition from the West to the East American district is even less marked; for the lapse of European and West American species is trifling, and the appearance of East American ones is equally so: the transition in vegetation from this district, again, to that of Greenland is as I have stated above, comparatively very abrupt.

The general uniformity of the arctic flora, and the special differences between its subdivisions may be thus estimated: the arctic Phaenogamic flora consists of 762 species; of these, 616 are Arctic European, many of which prevail throughout the polar area, being distributed in the following proportions through its different longitudes:—

This table places in a most striking point of view the anomalous condition of Greenland, which, though so favourably situated for harbouring an Arctic American vegetation, and so unfavourably for an Arctic European one, presents little trace of the botanical features of the great continent to which it geographically belongs, and an almost absolute identity with those of Europe. Moreover, the peculiarities of the Greenland flora are not confined to these; for a detailed examination shows that it differs from all other parts of the arctic regions in wanting many extremely common Scandinavian plants which advance far north in all the other polar districts, and that the general poverty of its flora in species is more due to an abstraction of arctic types than to a deficiency of temperature. This is proved by an examination of the temperate portion of the Greenland peninsula, which adds very few plants to the entire flora, as compared with a similar area south of. any other arctic region; and these few are chiefly arctic plants and almost without exception Arctic Scandinavian species.

There is nothing in the physical features of the arctic regions, their oceanic or aerial currents, their geographical relations, nor their temperature, which, in my opinion, at all accounts for the exceptional character of the Greenland flora; nor do I see how it can be explained, except by assuming that extensive changes of climate, and of land and sea, have exerted great influence, first in directing the migration of the Scandinavian species over the whole polar zone, and afterwards in introducing the Asiatic and American species with which the Scandinavian are so largely associated in all the arctic districts except those of Europe and Greenland. It is inconceivable to me that so many Scandinavian plants should, under existing conditions of sea, land, and temperature, have not only found their way westward to Greenland, by migration across the Atlantic, but should have stopped short on its west coast, and not crossed to America; or that so many American types should terminate as abruptly on the west coast of Baffin’s Bay, and not cross to Greenland and Europe; or that Greenland should contain actually much fewer species of European plants than have found their way eastwards from Lapland by Asia into Western and Eastern Arctic America; or that the Scandinavian vegetation should in every longitude have migrated across the tropics of Asia and America, whilst those typical plants of these continents which have found their way into the arctic regions, have. there remained restricted to their own meridians.

It appears to me difficult to account for these facts, unless we admit Mr. Darwin’s* [* This theory of a southern migration of northern types being due to the cold epochs preceding and during the glacial, originated, I believe, with the late Edward Forbes; the extended one, of their transtropical migration, is Mr. Darwin’s, and is discussed by him in his 'Origin of Species,' chap. xi.] hypotheses, first, that the existing Scandinavian flora is of great antiquity, and that previous to the glacial epoch it was more uniformly distributed over the polar zone than it is now; secondly, that during the advent of the glacial period this Scandinavian vegetation was driven southward in every longitude, and even across the tropics into the south temperate zone; and that on the succeeding warmth of the present epoch, those species that survived both ascended the mountains of the warmer zones, and also returned northward, accompanied by aborigines of the countries they had invaded during their southern migration. Mr. Darwin shows how aptly such an explanation meets the difficulty of accounting for the restriction of so many American and Asiatic arctic types to their own peculiar longitudinal zones, and for what is a far greater difficulty, the representation of the same arctic genera by most closely allied species in different Iongitudes. To this representation, and the complexity of its character, I shall have to allude when indicating the sources of difficulties I have encountered, whether in limiting the polar species, or in determining to what southern forms many are most directly referable. Mr. Darwin’s hypothesis accounts for many varieties of one plant being found in various alpine and arctic regions of the globe, by the competition into which their common ancestor was brought with the aborigines of the countries it invaded: different races survived the struggle for life in different longitudes; and these races again, afterwards converging on the zone from which their ancestor started, present there a plexus of closely allied but more or less distinct varieties or even species, whose geographical limits overlap, and whose members very probably occasionally breed together.

Nor is the application of this hypothesis limited to this inquiry; for it offers a possible explanation of a general conclusion at which I had previously arrived † [† Introd. Essay to the ‘Flora of Tasmania,' P. ciii.] and shall have again to discuss here -viz. that the Scandinavian flora is present in every latitude of the globe, and is the only one that is so; and it also helps to explain another class of most interesting and anomalous facts in arctic distribution, at which I have now arrived from an examination of the vegetation of the several polar districts, and especially of that of Greenland.

A glance at the appended chart shows how this theory bears upon the Greenland flora, explaining the identity of its existing vegetation with that of Lapland, and accounting for its paucity of species, for the rarity of American species, of peculiar species, and of marked varieties of European species. If it be granted that the polar area was once occupied by the Scandinavian flora, and that the cold of the glacial epoch did drive this vegetation southwards, it is evident that the Greenland individuals, from being confined to a peninsula, would be exposed to very different conditions to those of the great continents. In Greenland many species would, as it were, be driven into the sea, that is, exterminated; and the survivors would be confined to the southern portion of the peninsula, and not being there brought into competition with other types, there could be no struggle for life amongst their progeny, and consequently no selection of better-adapted varieties. On the return of heat, these survivors would simply travel northwards, unaccompanied by the plants of any other country.

In Arctic America and Asia, on the other hand, where there was a free southern extension and dilatation of land for the same Scandinavian plants to occupy, these would multiply enormously in individuals, branching off into varieties and subspecies, and occupy a larger area the further south they were driven; and none need be altogether lost in the southern migration over plains, though many would in the struggle that ensued when they reached the mountains of those continents and were brought into competition with the alpine plants, which the same cold had caused to descend to the plains. Hence, on the return of warmth, many more Scandinavian species would return to Arctic America and Asia, than survived in Greenland; some would be changed in form, because only the favoured varieties could have survived the struggle; some of the Alpine Siberian and Rocky Mountain species would accompany them to the arctic zone; while many arctic species would ascend those mountains, accompanying the alpine species in their reascent.

Again, as the same species may have been destroyed in most longitudes, or at most elevations, but -not at all, we should expect to find some of those Arctic Scandinavian plants of Greenland which have not returned to Arctic America still lurking in remote alpine corners of that great continent; and we may account for Draba aurea being confined to Greenland and the Rocky Mountains, Potentilla tridentata to Greenland and Labrador, and Arenaria Groenlandica to Greenland and the White Mountains of New Hampshire, by supposing that these were originally Scandinavian plants, which on the return of warmth were exterminated on the plains of the American continent, but found a refuge on its mountains, where they now exist.

It appears, therefore, to be no slight confirmation. of the general truth of Mr. Darwin’s hypothesis, that, besides harmonizing with the distribution of arctic plants within and beyond the polar zone, it can also be made, without straining, to account for that distribution and for many anomalies of the Greenland flora, viz., 1, its identity with the Lapponian; 2, its paucity of species; 3, the fewness of temperate plants in temperate Greenland, and the still fewer plants that area adds to the entire flora of Greenland; 4, the rarity of both Asiatic and American species or types in Greenland; and 5, the presence of a few of the rarest Greenland and Scandinavian species in enormously remote alpine localities of West America and the United States.

[BACK to top of page]

On the Local Distribution of Plants within the Arctic Circle.

The greatest number of plants occurring in any given arctic district is found in the European, where 616 flowering. plants have been collected from the verge of the circle to Spitzbergen. From this region vegetation rapidly diminishes in proceeding eastwards and westwards, especially the latter. Thus, in Arctic Asia only 233 flowering plants have been collected; in Arctic Greenland, 207 species; in the American continent east of the Mackenzie River, 379 species; and in the area westwards from that river to Behring’s Straits, 364 species.

A glance at the annual and monthly isothermal lines shows that there is little relation between the temperature and vegetation of the areas they intersect, beyond the general feature of the scantiness of the Siberian flora being accompanied by a great southern bend of the annual isotherm of 32° in Asia, and the greatest northern bend of the same isotherm occurring in the longitude of west Lapland, which contains the richest flora. On the other hand, the same isotherm bends northwards in passing from Eastern America to Greenland, the vegetation of which is the scantier of the two; and passes to the northward of Iceland, which is much poorer in species than those parts of Lapland to the southward of which it passes.

The June isothermals, as indicating the most effective temperatures in the arctic regions (where all vegetation is torpid for nine months, and excessively stimulated during the three others), might have been expected to indicate better the positions of the most luxuriant vegetation: but neither is this the case; for the June isothermal of 41°, which lies within the arctic zone in Asia, where the vegetation is scanty in the extreme, descends to 54° N. lat. in the meridian of Behring’s Straits, where the flora is comparatively luxuriant; and the June isothermal of 32° which traverses Greenland north of Disco, passes to the north both of Spitzbergen and the Parry Islands. In fact, it is neither the mean annual, nor the summer (flowering), nor the autumn (fruiting) temperature that determines the abundance or scarcity of the vegetation in each district, but these combined with the ocean temperature and consequent prevalence of humidity, its geographical position, and its former conditions both climatal and geographical. The relations between the isothermals and floras in each longitude being therefore special, and not general, I shall consider them further when defining the different arctic floras.

The northern limits to which vegetation extends varies in every longitude; and its extreme limits are still unknown; it may, indeed, reach to the pole itself. Phaenogamic plants, however, are probably nowhere found far north of lat. 81°. 70 flowering plants are found in Spitzbergen; and Sabine and Ross collected 9 on Walden Island, towards its northern extreme, but none on Ross’s Islet, 15 miles further to the north. Sutherland, a very careful and intelligent collector, found 23 at Melville Bay and Wolstenholme and Whale Sounds, in the extreme north of Baffin’s Bay (lat. 76°, 77° N.). Parry, James Ross, Sabine, Beechey, and others, together found 60 species on Melville Island, and Lyall 50 on the islands north of Barrow Straits and Lancaster Sound. About 80 have been detected on the west shores of Baffin’s Bay and Davis’s Straits, between Pond Bay and Home Bay. To the north of Eastern Asia, again, Seemann collected only 4 species on Herald Island, lat. 71½° N., the northernmost point attained in that longitude. On the west coast of Greenland, Scoresby and Sabine found only 50 between the parallels of 70° and 75° N.; whilst 150 inhabit the east coast, between the same parallels.

The differences between the vegetations of the various polar areas seem to be to a considerable extent constant up to the extreme limits of vegetation in each. Thus Ranunculus glacialis and Saxifraga flagellaris, which are all but absent in West Greenland*, [* Both were found by Kane’s Expedition, but by no previous one.] advance to the extreme north in East Greenland and Spitzbergen. Caltha palustris, Astragalus alpinus, Oxytropis Uralensis and nigrescens, Parrya arctica, Sieversia, Rossii, Nardosmia corymbosa, Senecio palustris, Deschampsia caespitosa, Saxifraga hieraciifolia and Hirculus, all of which are absent in West Greenland, advance to Lancaster Sound and the polar American islands, a very few miles to the westward of Greenland.

On the other hand, Lychnis alpina, Arabis alpina, Stellaria cerastioides, Potentilla tridentata, Cassiopeia hypnoides, Phyllodoce taxifolia, Veronica alpina, Thymus Serpyllum, Luzula spicata, and Phleum alpinum, all advance north of 70° in West Greenland, but are wholly unknown in any part of Arctic Eastern America or the polar islands.

The most arctic plants of general distribution that are found far north in all the arctic areas are the following; all inhabit the Parry Islands, or Spitzbergen, or both

Of the above, Saxifraga oppositifolia is probably the most ubiquitous, and may be considered the commonest and most arctic flowering plant.

The following are also inhabitants of all the five arctic areas, but do not usually attain such high latitudes as the foregoing:—

The absence of Gentiana and Primula in these lists is very unaccountable, seeing how abundant and very alpine they are on the Alps and Himalaya, and Gentiana on the South American Cordilleras also.

The few remaining plants, which are all very northern, and almost or wholly confined to the arctic zone, are the following. † indicates those species absolutely peculiar; †† the only peculiar genus.

[BACK to top of page]

On the Distribution of Arctic Flowering Plants in various Regions of the Globe.

There is but one distinct genus confined to the arctic regions, the monotypic and local -Pleuropogon Sabini; and there are but seven other peculiarly arctic species, to-ether with one with which I am wholly unacquainted, viz. Monolepis Asiatica. The remaining 762 species are all of them found south of the circle; and of these all but 150 advance south of the parallel of 40° N. lat., either in the Mediterranean basin, Northern India, the United States, Oregon, or California; about 50 are natives of the mountainous regions of the tropics; and just 105 inhabit the south temperate zone.

The proportion of species which have migrated southwards in the Old and New World also bear a fair relation to the facilities for migration presented by the different continents. Thus,

These tables present in a very striking point of view the fact of the Scandinavian flora being the most widely distributed over the globe. The Mediterranean, South African, Malayan, Australian, and all the floras of the New World have narrow ranges compared with the Scandinavian, and none of them form a prominent feature in any other continent than their own; but the Scandinavian not only girdles the globe in the arctic circle, and dominates over all others in the north temperate zone of the Old World, but intrudes conspicuously into every other temperate flora, whether in the northern or southern hemisphere, or on the Alps of tropical countries.

The severest test to which this observation could be put is that supplied by the Arctic Scandinavian forms; for these belong to the remotest corner of the Scandinavian area, and should of all plants be the most impatient of temperate, warm, and tropical climates. The following will, approximately, express the result

In one respect this migration is most direct in the American meridian, where more arctic species reach the highest southern latitudes. This I have accounted for (Flora Antarctica, p. 230) by the continuous chain of the Andes having favoured their southern dispersion.

But the greatest number of arctic plants are located in Central Europe, no fewer than 530 out of 762 inhabiting the Alps and Central and Southern Europe, of which 480 cross the Alps to the Mediterranean basin. Here, however, their further spread is apparently suddenly arrested; for though many doubtless are to be found in the Alps of Abyssinia and the western Atlas, these are few compared with what are found further east in Asia; and fewer still have found their way to South Africa.

The most continuous extension of Scandinavian forms is in the direction of the greatest continental extension; namely, that from the North Cape in Lapland to Tasmania*; [* The line which joins these points passes through Siberia, Eastern China, the Celebes Islands, and Australia, but the glacial migration has no doubt been due south from the arctic and north temperate regions in various longitudes to the Pyrenees, Alps, Carpathians, Caucasus, Asia Minor, Persian and North Indian mountains, &c. The further migration south to the distant and scattered alpine heights of the tropics, and thence to South Australia, Tasmania, and New Zealand, is, in the present state of our knowledge, to me quite unaccounted for. Mr. Darwin assumes for this purpose a cooled condition of the globe that must have been fatal to all such purely tropical vegetation as we are now familiar with.] for no less than 350 Scandinavian plants have been found in the Himalaya, and 53 in Australia and New Zealand; whereas there are scarcely any Himalayan and no Australian or Antarctic forms in Arctic Europe. Now that Mr. Darwin’s hypotheses are so far accepted by many botanists, in that these concede many species of each genus to have had in most cases a common origin, it may be well to tabulate the generic distribution of arctic plants as I have done the specific; and this places the prevalence of the Scandinavian types of vegetation in a much stronger light:–

The most remarkable anomaly is the absence of Primula in Tropical America, that genus being found in Extra-tropical South America; and its absence in the whole southern temperate zone of the Old World, except the Alps of Java.

Thalictrum, Delphinium, Impatiens, Prunus, Circaea, Chrysosplenium, Parnassia, Bupleurum, Hieracleum, Viburnum, Valeriana, Artemisia, Vaccinium, Rhododendron, Pedicularis, and Salix, are all arctic genera found on the tropical mountains of Asia (Nilghiri, Ceylon, Java, &c.), but not yet in the south temperate zones of Asia, and very few of them in Temperate South Africa.

There are, however, a considerable number of Scandinavian plants which are not found in the Alps of Middle Europe, though found in the Caucasus, Himalaya, &c.; and conversely there are several Arctic Asiatic and American plants found in the Alps of Central Europe, but nowhere in Arctic Europe. In other words, certain species extend from Arctic America through Central Asia and North India to Central Europe, which do not extend from Arctic America westward to Arctic Europe; and there are certain other species which extend from Arctic Europe to the Caucasus and Central Asia, which do neither exist on the Alp’s of Central Europe nor extend eastward to Arctic America: thus,

[BACK to top of page]

Common to Arctic Europe and Temperate Asia, &c., but not to Alps of Europe

[Long list of plants omitted, pp. 260–261 in the original.]

It is curious to remark how many of these boreal European plants, which are absentees in the Alps, have a very wide range, not only extending to the Himalaya and North China, but many of them all over Temperate North America; only one is found in the south temperate zone. In the present state of our knowledge we cannot account for the absence of these in the Alps; either they were not natives of Arctic Europe immediately previous to the glacial period, or if so, and they were then driven south to the Alps, they were afterwards there exterminated; or, lastly, they still inhabit the Alps under disguised forms, which pass for difierent species. Probably some belong to each of these categories. I need hardly remark that none inhabit Europe south of the Alps, or any part of the African continent.

The list of Arctic American and Asiatic species which do inhabit the Alps of Europe, but not Arctic Europe, is much smaller. Those marked † are Scandinavian, but do not enter the arctic circle.

[BACK to top of page]

[RETURN to list of writings]

[Welcome] · [Biography] · [Writings] · [Collectors] · [Links] · [Archives] · [Sources] · [Search] · [Site info]