2 Canadian Record of Science. 
CANADIAN GROUP. 
There are no temperate plants in Canada of wide range 
from Atlantic to Pacific, which are exclusively Canadian, 
but there are many species of which it may be predicated 
that their maximum distribution is in this country rather 
than in the Uuited States. The species which are common 
to Europe and America, and range to the Pacific, being 
chiefly northern temperate plants, have, as a rule, the mass 
of the individuals of each species in Canada. Exclusive of 
these, however, the following are illustrations of the 
group so 
Viola blanda, Willd. Alnus viridis, D. C. 
Lathyrus ochroleucus, Hook. Vicia Americana, Muhl. 
Potentilla arguta, Pursh. Geum triflorum, Pursh. 
Rubus triflorus, Rich. Rosa blanda, Ait. 
R. strigosus, Mq. Cornus stolonifera, Mx. 
Cornus Canadensis, L. Chiogenes hispidula, T. & G. 
Nardosmia palmata, Hook. Menyanthes trifoliata, L. 
Kalmia glauca, Ait. Shepherdia Canadensis, Nutt. 
Apocynum androszemifolium, L. Betula papyracea, Mx. 
Corylus rostrata, Ait. Smilacina trifolia Desf. 
The question naturally suggests itself—Why are many 
species of wide range, reaching from one side of the con- 
tinent to the other, whilst many others are circumscribed 
in area? It is quite clear that the size and weight of the 
seed, and the appendages which it may have in the shape 
of wings or silky plumes, to aid in its dissemination, the 
high winds, the crops, feathers and feet of birds, the dif- 
ferent relations of land and water and temperature in past 
ages—all have been important factors in the extension of 
the range of plants. But there is another conclusion, the 
drawing of which analogy warrants. Every plant may be 
said to have an area where the number of its species and 
the condition of its growth are at the maximum. Outside 
of this area, the individuals are found in diminishing numbers 
until their progress, varying in different directions, finally 
ceases on every side, The growth, again, of each individual 
