1903-4. | How Pant LIFE 1s DISTRIBUTED IN CANADA AND WHY, 27 
Cascade Group.—Embracing a well marked assemblage which is 
confined to the westerly side of Vancouver Island and to the vicinity of 
the Cascade range of mountains on the main land. 
Arctic Group.—Comprising a few rare representatives in the Alpine 
districts of New England, and on the Mingan Islands and Island of Anti- 
costi and neighbouring coasts, but as a rule confined to the high northern 
coasts of Labrador and Hudson Bay, and to Greenland, the shores of 
Baffin’s Bay, the Arctic Islands and Lower Mackenzie River country, 
and to the higher peaks of the mountains of British Columbia. 
European Group.—Comprising an extensive flora common to Europe 
and Canada and in many cases extending to Japan and Manchuria. 
The causes which give rise to these various groups, may be classed 
as general, affecting each one of them, and producing similar influences 
in other countries; and special, resulting from sets of circumstances 
peculiar to Canada or due to natural conditions prevailing there, either 
now or in past ages. After all our thought, however, there remain anoma- 
lies hard to explain and that will always afford food for speculation. 
GENERAL CAUSES OF DISTRIBUTION. 
The general causes, still in force, which have affected distribution 
are well known. River, lake and ocean currents, play their part in every 
section of the globe, not only in dispersing the seeds of aquatic plants, 
but also those of land species, which constantly come into connection 
with the water. The seeds are blown into the water and are carried 
sometimes long distances before they are again thrown upon the land by 
the waves. Thus, southern forms find their way northward, and northern 
forms meet with suitable localities farther south where the mass of water 
is sufficiently large to produce a cool, equable temperature. Particularly 
would this be the case in Canada where the water communications are 
on such an extraordinary scale, both on the coast line and along the Great 
Lakes and rivers in the interior of the country. Great mountain ranges, 
again, besides attracting moisture, form barriers to the distribution of 
plants, but on the other hand, as on the Rocky Mountains, provide 
facilities on their peaks, for the range southward of the Arctic flora. 
Birds form a constant source of distribution, going on for ages past. 
That seeds and fruits are the especial food of birds, that birds not only 
traverse great distances in search of food, but large numbers of them 
have semi-annual migrations, that the peculiar habits of birds lead them 
into situations where seeds may adhere to their feathers or in mud to their 
legs and feet, and that great numbers of seeds are for the purpose of 
diffusion supplied by nature with means of adhesion to objects, whether 
birds or quadrupeds, with which they are brought into contact, are all 
