THE ANCIENT OAKS OF AMERICA 
WILLIAM TRELEASE 
University of Lilinois 
While studying the oaks which are now so striking a component of 
the vegetation of North America, I have found it necessary to form 
some idea of the history of Quercus before our own day. Neither time 
nor opportunity has offered for basing this on a reexamination of the 
scattered materials that have served for the classic studies of Les- 
quereux and Newberry, or for the later work of Hollick, Knowlton, 
Berry and Cockerell; but from a careful examination of descriptions 
and illustrations I have tried to bring into some sort of orderly as- 
semblage the scattered facts that have been observed and described (1). 
So far as I know, only two of our fossil species (Q. consimilis and 
Q. paucidentata, both of the Eocene) are known in fruit (2); the others, 
though exceptionally with twig remnants, are represented usually by 
dissociated leaves, sometimes well preserved but frequently only in 
fragments showing little detail. These materials have been referred 
to Quercus because of the general appearance and especially the 
venation of the leaves when this is ascertainable. It is not sur- 
prising that misapprehension should have existed occasionally as to 
the age of clay and similar deposits in which some have been found, 
or that some of them should have been transferred to genera of other 
families, even, as a result of further study; indeed a considerable 
number of these fossils appear to have been called oaks rather because 
they could be called nothing else than for any very positive other 
reason (3). ' 
When the American fossils were first studied, the genus Quercus 
was made to include a number of forms that are segregated now in 
the genus Dryophyllum (4), held to be prototypic of the family Fagaceae 
rather than of its dominant genus, Quercus. The natural early tend- 
ency, as would be expected of conservative and experienced botanists 
working with isolated and fragmentary leaves, was to stretch the 
limits of species so as to recognize identities of Old and New World 
species, rather than to see dependable differences in such a repre- 
sentation, especially in a genus recognized as unusually variable in the 
foliage of even individual trees of existing species. None of the 
recently described species has been identified with a European form, 
and most of the earlier identities have been discarded, sometimes by 
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