Wherever the hygrometric, thermometric, telluric, and other conditions favor, the class of vegetation indicated by the presence of these conditions makes its appearance, just as the fire-weed makes its appearance in our warm temperate zone, not from the presence of seed, but simply the presence of "conditions"--the _pro_vision of man harmonizing with the _pre_vision of nature. In the same way the "Japan clover" made its appearance, as Professor Thurber states, "all over the southern states" during the late civil war, not from the migration of plants, but the presence of natural conditions.[16] The numerous facts we have already given, and many others that might be arrayed in advocacy of our position, taken in connection with the general facts here presented in regard to plant-distribution, all point directly to climatal and soil conditions as the real cause of dissemination, and not to their migration from continent to continent, and across vast intervening seas and oceans, as the theory of Professor Gray and others would require us to believe. Take the case of the _Schizoea pusilla_ of the New Jersey pine barrens, to which we have already referred, growing in similar barrens in New Zealand, and how are we to account for their antipodal appearance upon the globe? Professor Thurber refers to this plant as a "purely local fern" of New Jersey, and says it was for a long time supposed to be peculiar to that state until it was ascertained that it grew in New Zealand. Whether this plant "travelled" from New Zealand to New Jersey, or journeyed in the opposite direction, none of these "specific-centre" gentlemen can well inform us. Professor Agassiz would have said that it might have appeared, in numerous individuals, in both localities at the same time, or at different times, as conditions favored; and this would have been an exact scientific statement, no doubt, of the fact. Mr. Arthur Renfrey, and those who accept his scientific formulæ, must insist that this most beautiful of all our ferns was such a "favorite child of nature" that she condescended to create it _twice_ "in time and place," instead of only _once_. It is a poor rule, they may say, that has no exceptions in phenomenal manifestation.