VARIATION AND DISTRIBUTION OF SPECIES. 139 



This view once adopted, and this course once entered upon, 

 has to be pursued farther. Quercus Rohur of Europe with 

 its bevy of admitted derivatives, and its attending species 

 only provisionally admitted to that rank, is very closely 

 related to certain species of eastern Asia, and of Oregon and 

 California, — so closely that " a view of the specimens by no 

 means forbids the idea that they have all originated from 

 Q. Rohin\ or have originated, with the latter, from one or 

 more preceding forms so like the present ones that a natural- 

 ist could hardly know whether to call them species or varieties." 

 Moreover, there are fossil leaves from diluvian deposits in 

 Italy, figured by Gaudin, which are hardly distinguishable 

 from those of Q. Rohur on the one hand, and from those of 

 Q. Douglasii^ etc., of California on the other. No such 

 leaves are found in any Tertiary dej)osit in Europe ; but such 

 are found of that age, it appears, in northwest America, 

 where their remote descendants still flourish. So that the 

 probable genealogy of Q. Robur, traceable in Europe up to 

 the commencement of the present epoch, looks eastward and 

 far into the past on far distant shores. 



Q. Ilex, the Evergreen Oak of southern Europe and north- 

 ern Africa, reveals a similar archaeology ; but its presence in 

 Algeria leads De Candolle to regard it as a much more 

 ancient denizen of Europe than Q. Rohur ; and a Tertiary 

 Oak, Q. ilicoides, from a very old Miocene bed in Switzer- 

 land, is thought to be one of its ancestral forms. This high 

 antiquity once established, it follows almost of course that the 

 very nearly related species in central Asia, in Japan, in Cal- 

 ifornia, and even our own Live Oak with its Mexican rela- 

 tives, may probably enough be regarded as early offshoots 

 from the same stock with Q. Rex. 



In brief, — not to continue these abstracts and remarks, 

 and without reference to Darwin's particular theory (which 

 De Candolle at the close very fairly considers), — if existing 

 species, or many of them, are as ancient as they are now 

 generally thought to be, and were subject to the physical and 

 geographical changes (among them the coming and the going 

 of the Glacial epoch) which this antiquity implies; if in 



