﻿of Development of Vegetation on the Earth. 161 



plants sucli as oak and pine mingled with palms and other tropical 

 plants and with extra-European Sequoias, Cinnamons, Dryandras, etc. 

 Having worked out an explanation of this strange mingling on the 

 supjiosition that these were assemblages of plants brought together 

 which had grown at different elevations, Ettingshausen was led to 

 abandon that theory by a visit to the fossils in situ at Steiermark, 

 and became at once convinced that the Conifer<B, Betulacece and 

 CupuUfercB had not lived in zones above the Palms and Musacece, but 

 that the otherwise enigmatical association of these plants is easily 

 explained by supposing that the predecessors of our European 

 species, which differ from their descendants in many respects, were 

 able to exist in a warmer climate. 



In comparing the Tertiary Flora with that now living, Ettings- 

 hausen considers the former as a collective stock-flora, which may 

 be analysed into its component Flora-elements. Bj'' Flora-elements 

 he means all those ancient plant-forms whose representatives at 

 pi'esent belong exclusively to, and characterize some natural floral 

 region. 



The genetic relationship of some of the forest trees of the American 

 Continent, for example, to Tertiary trees can be traced directly from 

 horizon to horizon, as in the case of Castanea atavia to C. vesca. 

 In the development of our European Flora the analogues of trees 

 now living in America have played the most important parts. In 

 the Tertiary times the vegetation of the whole earth is supposed by 

 Ettingshausen to have had one and the same character, distinguished 

 by the general mixture of what he terms all the Flora-elements — as 

 far at all events as climatic conditions allowed, — which contained 

 witliin itself the elements from which all existing Floras are 

 derived.^ 



He characterizes these Flora-elements as chief-elements,- and col- 

 lateral-elements.^ For example, the Mid-European Flora-element 

 in the Tertiaries stands in reference to the existing Flora of Europe 

 as chief-element ; whilst all the exotic forms contained in the same 

 beds stand in the relationship of collateral-elements. We frequently 

 see certain plants taking their place in the natural Flora of a region 

 which appear extraneous to the general character of that Flora, some- 

 times even so abundantly represented as to influence the character 

 of the Flora. These are descendants of collateral-elements. 



Reference is then made to the Flora of Japan, which presents a 

 mixed assemblage of tree-forms, recalling forcibly the Flora of our 

 Tertiaries. In that place are to be seen growing side by side 

 apparent representatives of the vegetation of the East Indies and the 

 Amazons, of Europe and North America. 



The same mingling of types is seen, though less markedly, in the 

 woods of North America. The Southern States possess endemic and 

 European, Japanese and sub-tropical forms. In neither case could 

 this be the result of immigration. 



1 The Flora of America, it may be remarlied, is now known to liave been at least as 

 distinct from, that of Europe in Cretaceous (?) times as at present. — J. S. G. 



2 Haupt-element. ^ Neben-element. 



UECAUE II. VOL. IT. — NO. IV. 11 



