Notices of Memoirs—Prof. Boyd Dawkins’s Address, 461 
forests of France and Germany. They evidently were continuous 
both in space and time, from their beginning in the Upper Silurian 
to their decay and ultimate disappearance in the Permian age. This 
disappearance was probably due to geographical and climatic changes, 
following the altered relations of land to sea at the close of the 
Carboniferous age, by which Secondary plants, such as Voltzia and 
Walchia, were able to find their way by migration from an area 
hitherto isolated. ‘The Devonian formation is mapped off from the 
Carboniferous, and this from the Permian, but to a slight degree by 
the flora, and nearly altogether by the fauna. While the fauna 
exhibits great and important changes, the flora remained on the 
whole the same. 
The forests of the Secondary period, consisting of various Conifers 
and Cycads, also present slight differences as they are traced upwards 
through the Triassic and Jurassic rocks, while remarkable and 
striking changes took place in the fauna, which mark the division 
of the formations into smaller groups. As the evidence stands at 
present, the Cycads of the Lias do not differ in any important 
character from those of the Oolites or the Wealden, and the Salisburia 
in Yorkshire in the Liassic age is very similar to that of the Island 
of Mull in the Karly Tertiary, and to that (Salisburia adiantifolia) 
now living in the open air in Kew Gardens. 
Nor do we find evidence of greater variation in the dicotyledonous 
forests, from their first appearance in the Cenomanian stage of the 
Cretaceous rocks of Europe and America, through the whole of the 
Tertiary period down to the present time. In North America 
the flora of the Dakota series so closely resembles the Miocene 
of Switzerland that Dr. Heer has no hesitation in assigning it in the 
first instance to the Miocene age. It consists of more than one 
hundred species, of which about one-half are closely allied to those 
now living in the forests of North America—Sassafras, Tulip, Plane, 
Willow, Oak, Poplar, Maple, Beech, together with Sequoca, the ancestor 
of the giant Redwood of California. The first Palms also appear in 
both continents at this place in the Geological record. 
In the Tertiary period there is an unbroken sequence in the floras, 
as Mr. Starkie Gardner has proved, when they are traced over many 
latitudes, and most of the types still survive at the present day, but 
slightly altered. If, however, Tertiary floras of different ages are 
met with in one area, considerable differences are to be seen, due to 
progressive alterations in the climate and altered distribution of the 
land. As the temperature of the Northern Hemisphere became 
lowered, the tropical forests were pushed nearer and nearer to the 
Equator, and were replaced by plants of colder habit from the 
northern regions, until ultimately, in the Pleistocene age, the Arctic 
plants were pushed far to the south of their present habitat. In 
consequence of this Mr. Gardner concludes that “it is useless to seek 
in the Arctic regions for Hocene floras as we know them in our 
latitudes, for during the Tertiary Period the climatic conditions of 
the earth did not permit their growth there. Arctic fossil floras 
of temperate and therefore Miocene aspect are in all probability 
