mignonette (Reseda odorata), the date of introduction is not well ascertained; it has probably been a favourite border annual for sixty or seventy years, and yet it has in no degree shaken off its annual character, which is unnatural to it, and resumed the suffrutescent habit which it possesses in its own milder climate. The potato, too, which has for two centuries and a half been increased in every conceivable manner, by seeds as well as by offsets, bears cold in no degree more readily than it did in the sixteenth century. Nor does it appear to us probable, that acclimatizing, if practicable, is to be brought about by sowing seeds in northern latitudes through successive generations. We do not believe that plants will bear their seeds at all in a temperature much lower than that in which they have been located by the hand of Nature. The heat of a northern summer sufficiently approximates to that of the tropics, to be considered, with reference to vegetation, as the same, and it is during that season that the seeds of all plants are ripened; the conditions, therefore, under which the seeds of Tropæolum, for example, are produced in England, do not materially differ from those under which the same seeds are produced in Peru; if the season proves unpropitious in any considerable degree, they are not produced at all. How then can it be expected that seeds ripened under similar circumstances, but in different latitudes, should give birth to a progeny differing in any remarkable particular from their parents? In fact, in power of resisting cold, they do not differ at all. If such a capability were to obtained, it would be by inducing plants to ripen their seeds in winter. But if it is certain that nothing is to be gained in acclimatizing, by raising plants from seed through successive generations, [p166] it is no less true that many trees, which have been supposed to be incapable of surviving a northern winter, are now ascertained to be perfectly hardy, and that the power of enduring cold may be increased in others, by a judicious management of soil and situation.