956 Cretaceous Floras of Canada. 
In connection with the above table it should be understood that 
Tertiary floras, probably Miocene in age, are known in the interior 
of British Columbia, though they have not yet been recognized in 
the territories east of the Rocky Mountains. | 
Before leaving this part of the subject I would deprecate the 
remark which I see occasionally made, that fossil plants are of little 
value in determining geological horizons in the Cretaceous and 
Tertiary. I admit in these periods some allowance must be made 
for local differences of station, and also that there is a generic same- 
ness in the flora of the Northern Hemisphere, from the Cenomanian 
to the modern, yet these local differences and general similarity are 
not of a nature to invalidate inferences as to age. No doubt palæo- 
botanists seem obliged, in deference to authority, and to the results 
of investigations limited to a few European localities, to group 
together, without distinction, all the floras of the later Cretaceous 
and earlier Tertiary, irrespective of stratigraphical considerations, 
the subject lost its geological importance. But when a good series 
has been obtained in any one region of some extent, the case becomes 
different. Though there is still much imperfection in our knowl- 
edge of the Cretaceous and Tertiary floras of Canada, I think the 
work already done in Canada in connection with that of Lesquereux 
and Newberry in the United States, is sufficient to enable any com- 
petent observer to distinguish by their fossil plants the Lower, 
Middle and Upper Cretaceous, and the latter from the Tertiary- 
PHYSICAL CONDITIONS AND CLIMATE INDICATED BY THE CRE- 
TACEOUS FLORAS. 
In the Jurassic and earliest Cretaceous periods the prevalence, 
over the whole of the Northern Hemisphere and for a long time, 
of a monotonous assemblage of gymnospermous and Acrogenous 
plants, implies a uniform and mild climate and facility for inter- 
communication in the north. Toward the end of the Jurassic and 
the beginning of the Cretaceous, the land of the Northern Hemis- 
phere was assuming greater dimensions, and the climate probably 
becoming a little less uniform. During the close of this period oF 
at the beginning of the next, the dicotyledonous flora seems{to have 
been introduced, under geographical conditions which permitted @ 
warm temperate climate to extend as far north as Greenland. 
