[pENHALLow] NOTES ON TERTIARY PLANTS 69 



have extended far beyond Toronto during the Don period. 



We are now brouglit more particularly to consider the evidence 

 afforded by Larix itself. If we accept the present southern limit of 

 //. americana as lying within northern Pennsylvania, it would be located 

 in about 41° 30' N. Assuming that the extreme southern extension of 

 the species in Pleistocene time is correctly represented in the Dahlonega 

 clays, then it must have been pushed southward to latitude 34° 30', and 

 this position must have been reached during what is known as the Scar- 

 borough period. Since the Scarborough period the vegetation has 

 retreated northward to such an extent as to establish the present 

 southern limit of the species, involving a migration of about 480 miles. 

 But we find that the extreme southern limits of the terminal moraines 

 in Illinois are only about 300 miles from Dahlonega, whence it may be 

 inferred that Larix may have been pushed at least one hundred or one 

 hundred and eighty miles farther to the south, where its remains should 

 be looked for. It has already been pointed out that the osage orange 

 affords evidence suggestive of the idea that during the Don period its 

 highest northern limits may have been at least two hundred miles north 

 of Toronto, and it therefore becomes obvious that between the Don 

 period on the one hand and the Scarborough period on the other, the 

 movements of the ice sheet must have induced a migration of individual 

 species to the extent of about eight hundred miles. 



With respect to the more immediate question involved in our study 

 of the Dahlonega specimen of Larix, the facts thus far recited seem to 

 amply justify the conclusion that the clays in which it was found are 

 chronologically equivalent to the Pleistocene deposits of the north, 

 having been laid down during the Scarborough period. 



Early in February of the present year I received from Prof. Ralph 

 S. Tarr, of Cornell University, eight specimens of plant remains obtained 

 from a series of borings which were made at Ithaca, N.Y., for the pur- 

 pose of securing artesian wells. Unfortunately the majority of the 

 specimens were worthless for purposes of determination, on account of 

 their exceedingly fragmentary character, and it was therefore neces- 

 sary to concentrate attention upon only three of them. One proved 

 to be a small putamen of some dnipaceous fruit; one represented the 

 wood of the larch — Larix americana — and the third represented a pine, 

 apparently Pinus rigida. Prof. Tarr reports that there was an unusual 

 abundance of logs within the range of the borings, and it is to be 

 regretted that circumstances were not favourable to the collection of a 

 large number of workable specimens. The formation in which the 

 trees were found is of Pleistocene age, with a total thickness of 342 

 feet.^ The trees, however, occur only in the upper strata, the larch 



^ Artesian Well Sections at Ithaca. N.Y. Jn'l of Geol. XIL, 1904, 69-82. 



