432 MIOCENE PLANTS AND INSECTS. chap. xxii. 



logous forms, which urc so like the living ones that he sup- 

 poses the one to have been derived genealogically from the 

 others. He hesitates indeed as to the manner of the trans- 

 formation, or the precise nature of the relationship, "whether 

 the changes were brought about by some influence exerted 

 continually for ages, or whether at some given moment the 

 old types were struck with a new image." 



Among the homologous plants alluded to are forty species, 

 of which both the leaves and fruits are preserved, and thirty 

 others, known at jDresent by their leaves only. In the first 

 list we find many American types, such as the tuli^D-tree, 

 Liriodendron, the deciduous cypress, Taxodium, the red 

 maple, and others, together with Japanese forms, such as 

 the cinnamon, which is very abundant. And, what is worthy 

 of notice, some of these fossils so closely allied to living- 

 plants occur not only in the Upper, hut even some few of 

 them as far back in time as the Lower Miocene formations 

 of Switzerland and German}'', which are probably as distant 

 from the Upper Miocene or Oeninghen beds as are the latter 

 from our own era. 



Some of the fossil plants to which Professor Ileer has 

 given new names have been regarded as recent S2)ecies by 

 other eminent naturalists. Thus, Unger had called one of 

 the trees allied to the elm, Planera Bichardi, a species 

 which now flourishes in the United States. Professor Heer 

 had attempted to distinguish it from the living tree by the 

 greater size of its fruit, hut this character he confessed did 

 not hold good, when he had an ojDportunity (1861) of com- 

 jiaring all the varieties of the living Playiera Bichardi 

 which Dr. Hooker laid before him in the rich herbarium of 

 Kew. 



As to the " homologous insects" of the Upper Miocene 

 period in Switzerland, we find among them, mingled with 

 genera and orders now wholly foreign to Europe, some very 



