76 HOYAL SOCIETY OF CANADA 



A careful examination of the foregoing tables will serve to disclose 

 important facts relative to the nature of the climate which distinguished 

 the several ])eriods indicated. The vegetation of the Don Eiver period is 

 very i-emarkable in the testimony it attbrds as to a warmer climate. Of 

 the range of Acer pleistoeeniciim we know nothing, since it is impossible 

 at the present time to establish its proper affinity with any given existing 

 species. Pirea sitchensis is a determination of doubtful value, and, as 

 already ])ointed out, this species must be left out of consideration in 

 determining climatic conditions. Sahx must also be left out of consider- 

 ation, since we do not know the species, and thus are unable to decide 

 whether it represents northern or southern types. Taxus canadensis is a 

 species which to-day ranges as far south as Tsew Jersey, and much farther 

 north than the Don River, so that it may have foi-med an element of a 

 climate the same as now, or have grown in a climate either warmer or 

 colder. Ulmus racemosa i-anges southward to Missouri and Kentucky, 

 and its occurrence in CJntario brings it to the northern limit of distri- 

 bution, so that it must be regarded as a southern type. Ulmvs americana. 

 although a more northern type than the pi'eceding, is nevertheless chietlj' 

 found to the south of the Don, so that its occurrence in the region of 

 Toronto, brings it pretty well towards the northern limit of its range. 

 Quercus obtvsiloba is a distinctly southern type, having its highest northern 

 limits in Michigan, and reaching southward to Florida and Texas, becom- 

 ing more abundant in the southern portion of its area of distribution. 

 PiatanuH occidentalis is also a southern type, having its highest northern 

 limits in Canada in the valley of the Don, thence extending southward 

 through the United States. Picea nigra like Taxus canadensis, is a type 

 of plant which may have belonged to a climate either M^armer or colder 

 than that of Toronto, at the present day. It is found as far south as 

 Pennsjivania, and reaches far northward to the Arctic Ocean. It is, 

 therefore, an Arctic type, but of such a character than it may have formed 

 an element in the flora of a somewhat warmer climate than that of 

 Ontario. JLiclura aurantiaca is now found sparingly in southern Ontario, 

 and at least may be cultivated there. It is, nevertheless, a southern type, 

 since it is now found chiefly through the region from eastern Kansas to 

 northern Texas ; the evidence which it aflords, is thus of exceptional 

 value. Fraxinus quadrangulata in southern Ontario is also at its northern 

 limit of distribution, extending southward as far as Tennessee. Asimina 

 triloba is rare in Ontario, being found at only a few places along the 

 shores of Lake Erie. It is a southern type. 



Our enumeration thus shows that thei'e are nine species of plants 

 occurring in the Pleistocene of the Don, of which six, or sixty-six per 

 cent are distinctively of a more southern type than the vegetation at 

 present flourishing in the same region, while three, or thirty-three per 

 cent may readily have flourished in a climate as warm as that of New 



