H20 FOREST LANDS OF NORTHERN RUSSIA. 



the Ginko properly so called (Salislmria 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 Taxad the Torreya Dicksoniana, Heer a 

 remarkable species precisely determined, which proves 

 that the group of Taxineas 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 T. nucifera, Sieb. and 

 Zucc., 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. 

 Reichenbachii, 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 S. 

 gracilis, the S. gigantea, which is met with in the tertiary. 

 But by the side of this Sequoia there may be distinguished 

 yet others, and amongst them the S. Smithiana, which, with 

 the help of an intermediate series, connects itself without 

 any gap to the S. sempervirens of California. It is then 



