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in a collection of fossil plants from the Yukon valley, which were 
submitted to Dr. F. H. Knowlton, paleobotanist of the Survey, 
stratigraphical point of view, that Dr. Knowlton expressed his 
suspicion that specimens from different geologic horizons had 
been mixed—cycads, generically identical with Jurassic types, 
associated with well-known Cretaceous and Tertiary species of 
angiosperms, the aggregate apparently representing a mixture of 
tropical and temperate zone vegetation which was bewildering, 
besides sadly upsetting all our previous knowledge in regard to the 
integrity of the floras of the several geological periods mentioned. 
t was necessary, however, for the proper geologic mapping of 
the region that the facts should be definitely ascertained and 
aula and as this involved a paleobotanical cae 
I was deputed to visit the Yukon valley in 1903, make careful 
peleearie and collections, and endeavor, if see to 
settle the points at issue 
Mr. Collier’s locality was successfully located and I sent 
back from there, and from other localities scattered for a distance 
of about a thousand miles along the Yukon valley, some 1,800 
Ibs. of fossil plant specimens. The ultimate result was that 
Mr. Collier was vindicated. The association of floral elements 
was found to be exactly as his original collections indicated. 
In fact the cycads and angiosperms were ra , not only in the 
same strata but in the same layers of rock and occasionally so 
closely associated together that both a S included in one 
photog: nau 
Then came the problem of the geological age of the horizon in 
which nee diverse floral elements were associated. The facts 
were discussed and our final conclusions were that it was more 
the Jurassic cycads, had persisted into the Cretaceous than 
that the more highly developed type, represented by the es 
taceous angiosperms, had begun back in the Jur. 
therefore called the flora Cretaceous. Subsequent paniene ee 
