298 The Pliocene Flora of Transcaucasia. 



many times, but this material was sometimes replaced by a deposit 

 of porous volcanic substance cemented with clay. 



To what period can we assign these eruptions which were the 

 cause of the preservation of so rich and heterogeneous a vegetation ? 

 Where can we find either in the Caucasus or in other parts of the old 

 world an analogous formation 1 



The list we have given of the plant impressions from the " Fossil 

 Wood " suggests a comparison of the vegetation with the Tertiary 

 flora of Western Europe. In that flora we meet with species 

 characteristic of North America, tJie Canary Islands, also some 

 Asiatic and European forms. A similar combination of elements 

 is also met with, to some extent, in the upper Tertiary beds of 

 Switzerland (the Oeningen Series), but it is especially characteristic 

 of the Poutish beds of France, Germany, Austria, and Italy, also 

 the lower Pliocene flora (namely Plaisancien superieur) of the central 

 Massif of France. The Pliocene flora preserved in lava cinders 

 (gisements cineritiques) in beds associated with andesite lavas of 

 Pas de Mougudo and St. Vincent la Sabie in the Cantal ^ is the most 

 nearly allied to ours, and it also represents a falling off in the number 

 of known European forms in comparison with the Miocene flora. 

 According to Laurent in the flora he describes there is a striking 

 predominance of Lauraceae, Urticaceae, and Amentaceae.^ The 

 climate of the Cantal according to Laurent was almost that of an 

 island, soft, tropical, or sub-tropical and rather damp. 



If we compare these beds with our existing flora we are struck 

 by certain difieiences in facies ; the flora of the Godersky summit 

 is characterized by the absence of Northern Palaearctic elements 

 such as chestnut, beech, alder, ash, and other trees. On the other 

 hand, it should be pointed out that Paulownia and Oreodaphne, 

 which are very characteristic Pliocene genera, do occur in our 

 flora. If we compare our flora with those of the same Lower Pliocene 

 age in Europe we find similar forms in Pliocene beds of France and 

 the adjacent part of Spain (the ravine of Esplugas near Barcelona) 

 which contain a high jjercentage of similar types. ^ The species 

 common to our flora and the Franco-Spanish flora are : Aspidium 

 Meyeri Heer, Ficus muUmervis Heer, Cinnamomum Scheuchzeri 

 Heer, Eleagnus acuminata Web., Andromeda j^rotogaea Ung., 

 Berchemia midtinervis Heer, which is very close to our B. Wino- 

 gradowi sp. nov. Probably further analysis will reveal additional 

 types common to both floras. Lx France some palms have been found 

 in beds equivalent to ours. The average temperature of these places 

 was 17° to 18° C, as, for example, in Madeira and the Canary 

 Islands at the present day. The predominance in our flora of 

 mesophyll plants as well as ferns points not only to a warmer, but 



^ Laurent, Ann. Mus. d'TIist. Nat. Marseilles Geologie, t. ix, 1904-5. 

 2 Laurent, ibid., t. xii, 1908, p. 12. 



^ Laurent, Catalog de la Flora Pliocena de los Alrededores de Barcelona 

 (J. Almeda), Madrid, 1897. 



