186 BARWINIANA. 



to frequent and great changes of habitation or limita- 

 tion, but without appreciable change of specific form 

 or character ; that is, without prof ounder changes than 

 those within which a species at the present time is 

 known to vary. Moreover, he is careful to state that 

 he is far from concluding that the time of the appear- 

 ance of a species in Europe at all indicates the time of 

 its origin. Looking back still further into the Tertiary 

 epoch, of which the vegetable remains indicate many 

 analogous, but few, if any, identical forms, he con- 

 cludes, with Heer and others, that specific changes of 

 f orcn, as well as changes of station, are to be presumed ; 

 and, finally, that " the theory of a succession of forms 

 through the deviation of anterior forms is the most 

 natural hypothesis, and the most accordant with the 

 known facts in palaeontology, geographical botany and 

 zoology, of anatomical structure and classification: 

 but direct proof of it is wanting, and moreover, it 

 true, it must have taken place very slowly ; so slowly, 

 indeed, that its effects are discernible only after a lapse 

 of time far longer than our historic epoch. " 



In contemplating the present state of the species 

 of Cupuliferce in Europe, De Candolle comes to the 

 conclusion that, while the beech is increasing, and ex- 

 tending its limits southward and westward (at the ex- 

 pense of Coniferce and birches), the common oak, to 

 some extent, and the Turkey oak decidedly, are di- 

 minishing and retreating, and this wholly irrespective 

 of man's agency. This is inferred of the Turkey oak 

 from the great gaps found in its present geographical 

 area, which are otherwise inexplicable, and which he 

 regards as plain indications of a partial extinction. 



