236 THE POPULAR SCIENCE MONTHLY. 



temperature lias permitted them to maintain themselves sporadi- 

 cally. 



By regarding these considerations and this presumed march, 

 we succeed in determining the connection between recent and fos- 

 sil species, and evidences of affiliation between them. There also 

 exist relations not to be neglected between some recent types and 

 other old ones which we can not believe to be wholly lost, and 

 others between present forestal groupings taken separately and 

 those which have succeeded one another through the ages ; but 

 the further we go back, the more we address ourselves to a dis- 

 tant order of things, the less tangible are these relations found to 

 be. Of all the Carboniferous vegetation there remain only iso- 

 lated or dwarfed types, as of EquisetcB, ferns, and club-mosses. 

 The singular Japanese gingko, and perhaps the dammara of the 

 Indian Archipelago, can trace their ancestry back to that period. 

 A greater number of estrays have survived from the Secondary 

 ages ; but they are still rare — auracarias, cedars, pines, thuyas, and 

 a few colonies of cycads south of the equator. There has been 

 something vague and undetermined about the " foliage " trees since 

 they first appeared in the Cretaceous period ; but their evolution 

 and characteristic physiognomy have been tending to fix them- 

 selves. The magnolia, tulip-tree, plane-tree, ivy, etc., have hardly 

 varied since then ; but the subsequent modifications of other Eu- 

 ropean flora have been so frequent and profound that no collec- 

 tion of existing species corresponds excejjt by partial traits that 

 have been questioned with the Cretaceous vegetation. The cor- 

 respondence is somewhat closer with the vegetation of the Eocene, 

 especially of the later Eocene. The examination of certain floras 

 which are referred to this horizon has shown that vegetation has 

 not varied much since then, except from the impoverishment 

 which it has suffered by the subsequent elimination of some types, 

 and the addition of a number of deciduous types of later intro- 

 duction. Thus, a considerable proportion of forms, the ancestors 

 of which appeared in the Eocene, have persisted in place from 

 that epoch, while those which have since migrated are found in 

 more southerly regions. 



It is in the Miocene, particularly in the later Miocene, that the 

 relations become manifest of the deciduous trees of southern habit 

 which we have spoken of as being dispersed over various points of 

 the Mediterranean domain — the plane-tree, the liquidambar, the 

 planera, the linden, the vine, some hornbeams and ashes, the date- 

 palm, the pomegranate, etc. ; and the lauriferous grouping of the 

 Canary Islands, preserved intact by means of its insular situa- 

 tion and of the persistency of local climatological conditions, re- 

 produces unchanged the picture of a mountain-forest of central 

 Europe, as recent discoveries have shown it to have been in the 



