5 : 
utterly incompatible with" fern life, though the island-like snow- 
covered mountain ridges which here and there emerge from the 
vast expanse of the thirsty plains, occasionally give shelter to a few 
hardy species. 
But, as we approach the western borders of the continent, the 
noble coniferous forests of the Cascade Mountains and of the 
Sierra Nevada again offer inviting conditions, and accordingly we 
have here a larger proportion of terns than we have seen since leav- 
ing the Appalachian regions. In California, the dry plains which 
lie between the Sierras and the coast range, again interrupt the 
fern-life which, however, re-appears upon the coast range. As we 
go northward along this western coast, the rains become more 
abundant and’ the ferns more luxuriant; bat as we go towards 
Southern California, aridity again prevails, restricting the number 
of species and individuals, and modifying their types. Abundant 
as is the fern-growth of Alaska, Washingten, and Oregon, the num- 
ber of species is much less than upon the Eastern border of the 
continent. A few species are peculiar, while the remainder are 
Asiatic forms which seem to have made their way across the Straits 
or over the Aleutian Isles even as far south as.California, there meet- 
ing a few types which have their homes in the Andes, — 
The number of species which inhabit North America as here de- 
fined, is about 125. They may be arranged in six geographical 
divisions, viz: 1. Cosmopolitan; 2. Boreal; 3. Appalachian; 4. 
Pacific ; 5. New Mexico or Central; 6. Tropical. In enumerating 
the species we italicize those which are also found in the old world. 
L Cosmoporiran: widely distributed over the ‘globe, in both 
temperate and tropical regions. 
Pteris aq a, L. Asplenium Trichomanes, L. : 
The first of these, thriving in sandy barrens, occurs abundantly 
in both the old and new world and in the islands, from Lapland 
in the north to New Zealand and Tasmania in the south. In North 
America it extends from Labrador and Alaska southward to the 
isthmus, avoiding only the arid and alkaline plains of our western 
interior. The other species of this group thrives only in the cre- 
vices of shaded rocks, and this condition only, seems to limit its 
distribution. Throughout the globe it is represented almost as 
universally as the Pteris. There are a few others of our species 
which are so widespread as almost to claim a place in this division 
but which it will be more convenient to consider in the other 
groups. : 
Il. BorEat: inhabiting (with a few exceptions) the northern 
portion of the United States, extending throngh Canada and Brit- 
ish America, some species even reaching Labrador, Greenland and 
Alaska, and nearly all represented also in the northern portions of 
the old world. ears 
Phegopteris polypodioides, Fée. = a ae 
apes) Bie, ie on a) ein, 
Germanica, Willd. o , 
