The oak family can be traced back to the Miocene period, and consequently enjoys quite as high an antiquity as the sequoias. Professor Gray, in speaking of the _Quercus robur_ and its probable origin, says that it is "traceable in Europe up to the commencement of the present epoch, looks eastward, and far into the past on far-distant shores." By "far-distant shores," he undoubtedly means Northwest America, where its remotest descendants still flourish. But that these trees should have waded the Pacific, or sent their acorns on a voyage of discovery after new habitats on the Asiatic coast, is hardly more probable than Jason's voyage after the golden fleece, in any other than a highly figurative sense. The spontaneous appearance of a forest of oaks on the eastern shores of Asia was just as probable, under favoring conditions--though occurring subsequently to the time of their appearance on this continent--as that of the miniature forests of "samphire," or small saline plants, which spontaneously made their appearance about the salt-works of Syracuse, when conditions actually favored. The high antiquity of the oak makes no difference in respect to the principle of dispersion, since geographical conditions are what govern, and not the theoretical considerations of the speculative botanist. Mr. A. R. Wallace's formula concerning the origin of species, that they "have come into existence coincident both in time and place with preëxisting closely-allied species," may or may not be true so far as individual localization is concerned. But it proves nothing in the way of original progeny, nor can we, by any actual data before us, satisfactorily determine, under this formula, which of the two closely-allied species preceded the other. If they came coincidently, both in time and place, their existence must have been concurrent, not separated by preëxistence. The formula may be true to this extent, that the conditions favoring the appearance of one species may have equally favored what we call a closely-allied species. But even in this case, the material sequence is lost, and we have nothing to express a relationship as from parent to progeny. For, however restricted as to localization, each species preserves its own characteristics, the similarities always being less than the dissimilarities. These, and other equally conclusive facts of observation, led Professor Agassiz to question any necessary genetic connection between the different species, or between even the same species, in widely-separated localities; his idea being precisely that advanced by us in connection with the Bible genesis, that localization depended on geographical conditions, not on the migration of plants or the dispersion of seeds.