II. OBSERVATIONS ON THE VEGETATION OF THE NORTHERN SHORES OF LAKE SUPERIOR. THE vegetation of the Northern shores of Lake Superior agrees so closely with that of the higher tracts of the Jura, which encloses the lower and middle zone of the subalpine region, that on glancing at the enumeration below, one is astonished to find so great a number of species entirely identical. Making full allowance for the influence of the lake, and leaving out of consideration a small number of species peculiar to North America, there remains about Lake Superior a subalpine flora which is almost identical with that of Europe, with which it is here compared. Although this fact is very striking, it is nevertheless in accordance with the general laws of botanical geography, and is another proof that the vegetation of the two continents becomes more and more homogeneous the more we advance northwards. I have divided the catalogue of the phænogamous plants collect ed about Lake Superior into four lists: The first containing such plants as are really subalpine in their character, or correspond to those of the forests of the lower Alps;* the second containing the plants of the lake proper, or the aquatic plants; † the third comprising the plants purely American,‡ and the fourth the cosmopolitan plants, or those which extend beyond the subalpine region. In the different Only such plants are introduced in the first list as have true representatives in Central Europe. +Lacustrine Flora and Fauna present so many peculiarities that it has been thought best to separate the plants of the lake, which are aquatic, from those of the main land enumerated in the first list. Besides the plants which have true analogues in Europe, there are some about Lake Superior which are truly American types; these constitute the third list. lists I have indicated as nearly as possible the analogous species whose location is the same in Europe.* SUBALPINE PLANTS OF LAKE EUROPEAN PLANTS OCCURRING IN SUPERIOR. RANUNCULA CEE. Anemone sylvestris L. In Europe the Anemones are for the most part alpine plants, but those only whose carpels are plumose, and which ought to be generally considered as a peculiar genus. Anemone sylvestris, the only European species which agrees with the American ones, occurs in the plains. Ranunculus repens L. Jura and Alps. In the Alps it rises to the height of 4,000 feet. Thalictrum minus L. Creux du Vent. Actæa spicata L. Woods of the higher Jura. CISTA CEE. Helianthemum vulgare J. Pastures of the lower Alps and Jura. All the plants enumerated below were collected by me and some of the gentlemen of our party, who took particular interest in the study of botany, as C. G. Loring, Jr., T. M. Lea, J. E. Cabot and Dr. Keller. They were for the most part determined on the spot with the excellent work of my friend Prof. Asa Gray on the Botany of the Northern United States. Afterwards my collection was revised by Dr. Gray himself, and by Messrs. Leo Lesquereux and Ed. Tuckerman; the latter of whom examined the lichens with particular care, while Mr. Lesquereux revised more particularly the mosses, and furnished me with very minute information about the distribution of plants in Switzerland, to which I had myself paid a good deal of attention in former years. I owe it nevertheless to his contributions upon this particular point, that I have been able to carry my comparisons of the plants of Lake Superior and Central Europe so much into detail as I have done. Prof. Gray has also furnished me with very important documents respecting the distribution of many species, beyond the regions I have examined myself. The general views, however, derived from this study, as I have expressed them in the preceding and following pages, so far as they are new, are my own. This and several other plants of this list have a rather extensive range southwards; but this seems to be in accordance with the general direction of the mountain chains and the form of the American continent itself, in w ich both animals and plants peculiar to the arctic and temperate zones extend farther south, than their analogues in the Old World. It is a remarkable fact, that the family of Caryophyllaceæ, so extensive in the alpine regions of Europe, has so few representatives about Lake Superior. The reason is, that the Caryophyllaceæ, like the Cruciferæ, belong for the most part, to the alpine flora properly, and to the flora of the plains, and are missing in the subalpine, or intermediate regions. * A small species of Draba with yellow flowers, found at Michipicotin, was lost. LAKE SUPERIOR. ANA CARDIACEE. EUROPE. Rhus Toxicodendron, and several oth- Rhus Cotinus L. does not correspond er species which were not collected. to any of the North American species. The Malvacea are generally plants of warm countries. This family is not represented about Lake Superior by a single species, nor are the intermediate families between this and the Leguminosa. The Leguminosa themselves are very rare, since they are, like the Caryophyllaceæ, plants of the higher Alps, or of the plain. The Rosacea, on the contrary, generally extensive in the subalpine regions of Europe, are also abundant around Lake Superior. |