354 On the Temperature of Geological Periods. 



This intermittence is one of the principal phases of the alterna- 

 tions which we remark in the ancient vegetation, without being 

 able yet to define them exactly. Nothing, I again repeat, indi- 

 cates that the temperature was then sensibly lowered ; but it 

 is remarkable that the European genera seem to have been 

 favoured in their origin by the very circumstances which were 

 unfavourable to the Australian types, and especially to the 

 Proteacese*. The latter, indeed, like the Cycadese themselves, 

 as is proved by the presence in the Miocene of Zamites cpibius, 

 Sap. (Bonnieux), Lomatites aquensis, Sap. (Bonnieux, Manosque), 

 and Grevillea anisoloba, Brong. (Koumi), did not disappear en- 

 tirely until the European genera had become developed so as to 

 occupy an important place in the vegetation. 



About this period (that is to say, after the Tongrian) the new 

 revolution seems to have been completely achieved; the various 

 groups of the vegetable kingdom occur in Europe combined 

 pretty nearly as they are in the most favoured subtropical re- 

 gions of the existing world. 



The richness of this vegetation, of which the flora of Armissan 

 and subsequently that of (Eningen furnish us two magnificent 

 specimens, is very great. We must not, however, conclude from 

 it that the vegetable forms of the whole world were then united 

 in Europe — though the Europe of that period would have no occa- 

 sion to envy the most luxuriant of existing countries. Latitude 

 as yet exerted its influence only in a feeble manner. The palms, 

 which were very numerous in southern Europe along the shores 

 of that sea of the Mollasse which cut through its centre, became 

 less numerous to the north of that sea; the Laurinese, which 

 were there very abundant, penetrated to the neighbourhood in 

 which the Baltic now exists, where a leaf of Cinnamomum has 

 been found in a piece of amber ; Cupressinese, probably of the 

 genus Thujopsis, of which this substance was the resin, formed 

 beyond, in conjunction with pines, vast forests; further still 



* We must insist upon this double fact, which is so conclusively 

 proved by the organic evolution of the vegetable types which seem at 

 present reciprocally to exclude each other : the pines and cedars, Coni- 

 ferse now proper to the boreal zone, appear in Europe from Secondary 

 times in the midst of Aravcarice, Proteacesp, and forms of Cycadeae which 

 are no longer observed except in the southern hemisphere ; on the other 

 hand, these latter types do not finally quit our soil until the Tertiary epoch 

 is already far advanced. Thus the existing boreal types made their ap- 

 pearance in the midst of vegetation to a great extent Austrahan, and the 

 Australian types disappeared from our zone only when the European vege- 

 tation had already acquired the physiognomy w'hich distinguishes it. It is 

 therefore only in the course of long periods that the various vegetable com- 

 munities have been constituted and differentiated by the progressive deve- 

 lopment of their characteristic elements, and the slow elimination of those 

 which have become foreign to them. 



