CLIMATIC DISTRIBUTION OF CERTAIN ANGIOSPERM LEAVES 
37 
a few Cretaceous and Tertiary floras. As is well known, herbaceous 
Dicotyledons are of very infrequent occurrence as fossils below the 
upper Tertiary. In fact, the bulk of the leaves, of which we have a 
fossil record, seem to have belonged to arborescent or comparatively 
large woody species. Therefore, a study of the leaf-margins of Cre- 
taceous and of Tertiary floras of Dicotyledons should afford a rough 
index of the general climatic conditions which prevailed in the region 
where the floras existed. 
Table VI 
Tertiary Floras 
Entire, Percent 
Florissant, Kirchner, Upper Miocene 33 
Green River, Lesq., Upper Eocene 29 
John Day Basin, Knowlton, Upper Eocene 28 
Spitzbergen, Heer, Upper Eocene 46 
Arctic, Heer, Upper Eocene 29 
Bad Lands, Lesq., Lower Eocene 29 
Wilcox, Berry, Lower Eocene 83 
Cretaceous Floras 
Entire, Percent 
Montana, Knowlton 62 
Patoot, Arctic, Heer 51 
Atane, Arctic, Heer 81 
Dakota, Lesq 54 
Raritan, Berry 71 
A comparison of the first six Tertiary percentages, given in this 
table, with those of modern floras indicates very clearly the general 
temperate character of the climates that prevailed in the regions 
where these fossil floras existed. Similarly, the percentages of non- 
entire leaves in the Patoot and Dakota Cretaceous formations denote 
conditions intermediate between those of typical lowland-tropical 
and mesophytic cold-temperate climates. The Wilcox flora which, 
as has been shown by Berry, was a tropical strand flora, is in marked 
contrast to the more northern or temperate Tertiary floras. The high 
percentages of entire-leaved forms (megaphyllous) in the Atane beds 
points to the tropical character of the climate that existed in certain 
arctic regions during parts of the Cretaceous. 
Of course, caution is needed in comparing any percentage in this 
table with that of a living flora. This is due to the fact that one 
cannot always be certain that any known fossil flora is a fair sample 
