SPECIES AS TO VARIATION, ETC. 189 



before the present separation of Sicily, Sardinia and 

 Corsica, and of Britain, from the European Continent. 



This view once adopted, and this course once 

 entered upon, has to be pursued farther. Quercus 

 Robur of Europe with its bevy of admitted deriva- 

 tives, and its attending species only provisionally ad- 

 mitted 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. Rdbur, or have originated, with the latter, 

 from one or more preceding forms so like the present 

 ones that a naturalist 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. Robur on the one hand, and from those of Q. 

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

 leaves are found in any tertiary deposit in Europe ; 

 but such are found of that age, it appears, in North- 

 west America, where their remote descendants still 

 nourish. 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. 



Quercus Ilex, the evergreen oak of Southern Europe 

 and Northern 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. 

 Robur ; and a Tertiary oak, Q. ilicoides, from a very 

 old Miocene bed in Switzerland, is thought to be one 

 of its ancestral forms. This high antiquity once 



