Chapter IX — 147— On Migration 



with the dimatic conditions prevailing in the greater part of its present 

 area (Chevalier, 1927). 



Another plant which, as regards its time of flowering, likewise does 

 not find itself in accord with present-day habitat conditions is Col- 

 chicum Biebersteinii, distributed in Asia Minor, on the Balkan penin- 

 sula, in the southern part of the U.S.S.R., and in the Crimea. The 

 genus Colckicum has been divided into two subgenera, the more ancient 

 Archicolchicum and the more recent Eucolchicum (Stefanov, 1926). 

 Colckicum Biebersteinii belongs to the former, i.e., the more ancient, 

 subgenus. In the Crimea occasional specimens are found both in 

 steppe and mountain districts, on steppe and sandy soils. The cause 

 of its scarcity here lies in its very early flowering, beginning in Janu- 

 ary, i.e., in the very coldest month of the year in the Crimea, and 

 ending in March, when the flowering of other Crimean plants has only 

 just barely begun. 



The family Ericaceae, which has undoubtedly been preserved in 

 Europe since the Tertiary period, is characterized by the xerophytic 

 structure of its leaves, corresponding to the character of its habitats in 

 regions with a winter period of rainfall and in mountainous districts 

 but not at all in accord with its habitats in swampy localities. For 

 instance, the common north European heather, Calluna vulgaris, has 

 leaves with a structure markedly xerophytic in character. This species 

 is now very widely distributed, ranging from Spain, the Azores, and 

 Morocco to Norway, Lapland, and West Siberia. In the U.S.S.R. this 

 species extends as far south as Tula Region, being distributed, however, 

 chiefly in the northern regions. Fossil deposits of this heather have 

 only been found beginning with the Ice Age, so that we know nothing 

 regarding its distribution and migrations prior to the Quaternary 

 period. Nevertheless, it is very clear that its xerophytism is a fixed 

 peculiarity of structure that originated under entirely different habitat 

 conditions than those now prevailing over the greater part of its area. 



Another tj^e of disharmony we find in Erica carnea, belonging to 

 the same family and growing in the alpine zone of western Europe. 

 Its inflorescences develop only toward the end of summer, so that its 

 flowers are not ready for opening before the onset of cold weather, 

 which hinders the further development of the plant. It remains dor- 

 mant, under the snow cover, until spring, when, with the coming of warm 

 weather, it renews its development and its flowers open. This species, 

 closely related to Erica mediterranea, in the Tertiary period 

 undoubtedly did not have such a break in its development, since 

 climatic conditions were more uniform at that time (Chevalier, 1927). 



The genus Vacciniuni, most of whose representatives grow in the 

 tropics, has a few species that grow in temperate and subarctic zones 

 of the northern hemisphere, both in the Old and New Worlds, these 

 species no doubt being remnants of a Tertiary, probably mountain, 

 flora. The leaves of most species of Vaccinium, even of our north 

 European species — V. nigrum, V. Vitis idaea, V. uliginosum — or of the 

 mountain species, Arctostaphylos Uva-ursi, which extends to an altitude 

 of 2,000 m., and also of species of Oxycoccus, are thick, coriaceous, and 

 evergreen, in no way corresponding to the foliage of most other plants 

 of northern zones. That these are remnants of a Tertiary flora is testi- 



