E. V. Wulff 



—192- 



Historical Plant Geography 



stages by a great abundance and diversity of conifers, is during the 

 third stage characterized by extreme poverty as regards conifers. 



For a confirmation of Wegener's theory it is exceptionally im- 

 portant to establish correspondence or lack of correspondence between 

 the past distribution of plants and present-day climatic zones. As we 

 have already noted, Koppen and Wegener believe that during the 

 Cretaceous period and the beginning of the Tertiary period the tropical 

 zone occupied a different position than it does at present. By glancing 

 at the location of fossil occurrences of conifers, one is immediately 

 struck by the fact that, besides the marked zonation of their distri- 

 bution, they are found in the present-day arctic region in places located 

 beyond the northern limit of distribution of woody plants and now 

 lying under a permanent cover of snow and ice. Thus, according to 

 data presented by Koppen and Wegener, on Spitsbergen there have 



o 



Zoco/y^oa^ /'ey'o/rj &t//'/f?y Me 0//yocef7e- ^/'ocsffO. 



Fig. 34. — The distribution of Ginkgo adiantoides Unger in different geologic periods. 

 The geographic network and the shapes of the mainlands are those of the Eocene. The 

 distribution was effected by means of the connections between continents. The map 

 shows the progress of distribution during the Jurassic, the Cretaceous, and the Eocene, the 

 region in which the plant was locaUzed during the OUgocene-Miocene, the ginkgo area 

 which remained in Europe to the end of the Pliocene, and the Quarternary ginkgo area. 

 (After Shaparenko). 



been found fossil remains of 179 species of woody plants, conifers 

 predominating; in the western part of Greenland, as far north as 

 yo°N.— 169 species; on the Island of Disko— 282 species, of which 

 19 are ferns, 28 conifers, and 200 dicotyledons. Moreover, all these 

 fossil woody plants are characterized by annual rings. In deposits of 

 the end of the Tertiary period this type of vegetation in the arctic 

 region begins to disappear and in the Quaternary period it vanishes 

 altogether. At this time in the Antarctic there was still a subtropical 

 climate, as is attested by the finding there, in Quaternary deposits, of 

 Araucaria Nathorstii; the Falkland Islands were still heavily wooded 

 and Seymour Island, now lying in a region of eternal ice, was also 



