220 FOREST LANDS OF NORTHERN RUSSIA. 
the Ginko properly so called (Salishuria Arctica and S. 
grandis), and that of the Baiera and Jeanpaulia with 
lanceolate leaves with narrow segments, represented here 
by the Sclerophyllina cretosa, Schenk., and S. dichotoma, 
Heer. But alongside the Salisburias appears for the first 
time a veritable Tarad—the Torreya Dicksoniana, Heer—a 
remarkable species precisely determined, which proves 
that the group of Zaaineas proper had its cradle in the 
north, and that, after having dwelt a long time there, it 
passed thence into Europe, into America, and into Asia. 
Europe does not possess, it is true, the genus Torreya, but 
this genus has certainly lived there aforetime; and, in 
concert with Professor Marion, I have lately determined it 
in the pliocene tuffas of Meximieux under a form which it 
is difficult to separate from the 7. nucifera, Sieb. and 
Zuce., of Japan. The Glyptostrobus and the Sequoia have 
followed a course in every respect alike. The Glyptos- 
trobus Groenlandicus, Heer, is indeed the direct ancestor 
of G. Ungeri, Heer, and G. Europaeus, Brongn., which 
abounded in the Arctic zone in the time of the Lower 
Miocene; these two sister forms—forms slightly modified 
from the same type, spread themselves in Europe, and 
without doubt throughout the whole temperate zone in 
the course of the Miocene. Subsequently they disappeared 
from our continent, where, however, the G. Europaeus still 
lived towards the middle of the pliocene times, But 
to-day Southern China possesses, under the name of G. 
heterophyllus, a descendant scarcely modified from the G. 
Ungeri of the tertiary period. 
‘The chalk is veritably the age of the Sequoia. The S. 
Reichenbachit, Gein., obtained then an immense extension ; 
it is found everywhere in Europe in the middle chalk and 
in the superior chalk. It approaches, as does the 8S. 
gracilis, the S. gigantea, which is met with in the tertiary. 
But by the side of this Seguoia there may be distinguished 
yet others, and amongst them the 8. Smithiana, which, with 
the help of an intermediate series, connects itself without 
any gap to the S. sempervirens of California. It is then 
