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Show 188 ' DARWINIAN A. pubescens and are theref~re forms gJ.·ouped around these as ;ent~es; and, moreover, the few conneeting f orms are by no means the most common. We. re these to die out, it is clear that the three forms wh1.ch l1 ave ah·eady been so frequently tafik en for . s. pemlle s would be what the group of four or ve prov1s10na y admitted species which closely surround Q. Ro~ur now are. The best example of such a case, as havmg in all probability occurred through geographical segregation and partial extinction, is that of the cedar, thus separated into the Deodar, the Lebanon, and the Atlantic cedars-a case admirably worked out by Dr. Hooker two or three years ago.1 A special advantage of the Oupul'j/~T(]3 for ~ete.rmining the probable antiquity of ex1stmg spemes m Europe, De Candolle finds in the size ~nd character of their fruits. However it may be w1th other plants (and he comes to the conclusion generally that marine currents and all other means qf distant transport have played only a very small pa1~t in the actual dispersion of species), the transport of acorns an~ chestnu~s. by natural causes across an arm of the sea 1n a cond1hon to germinate and much more the spontaneous estab- . lishment of ~ forest of oaks or chestnuts in this way, De Candolle conceives to be fairly impossible in itself, and contrary to all experience. From such considera. tions, i. e., from the actual dispersion of the exis~ing species (with occasional aid from post-te.rti~ry de;os1ts~, it is thouOo 'ht to be shown that the prmmpal Cupu. h-feT(] 3 of the Old World attained their actual extensiOn t Natural History Review, January, 1862. SPECIES AS TO VARIATION, ETO. 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. Queraua Robur 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. Robur, 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. JJouglasii, 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 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. Quercus .llPiiJ, the evergreen oak of Southern Europe and N orthe.rn Africa, reveals a similar archreology ; 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. iliaoides, from a very old Miocene bed in Switzerland, is thought to be one of its ancestral forms. This high antiquity once 9 |