ACCLIMATION OF PLANTS. It is a gen erally received opinion that a plant removed from a warmer to a colder climate gradually becomes changed so that it will stand a lower temperature than in its native habitat. Such, however, is not the fact. Its zero, that is, the temperature at which it is killed, remains the same. The tem perature at which a plant is destroyed, varies with each species. Indian corn, for instance, is certainly killed when the thermometer sinks to 32° Fahrenheit. The cucumber is killed at 40°; the egg-plant at 45°. Celery, on the other hand, will withstand a temperature of 20°, and cabbage 15° or less. Plants, however, are essentially modified by being removed to a climate more severe than is natural to them. They gradually become earlier in ripening. Thus we see corn and potatoes, two of the plants most widely dis tributed as to latitude, broken up into a great number of varieties, some of them remarkably early in ripening. A contributor in an extended article on the geography of plants, originally published in a report of the Department of Ag riculture, holds the following language: We are apt to suppose that plants which grow in tropical countries must necessarily be tender, and adapted only to hot-house culture, not reflecting that they may have grown in very elevated and cold re gions in those countries. Such is the case with many species introduced from Japan, Chili and Nepal, which appear to be hardy in England. Of the dahlia, the heliotrope, the potato, and Lima bean, it may be said long culture has done nothing to increase their hardiness. Sound views respecting the geography of plants would correct the prevailing errors regarding accli mation. The acclimatizing of plants, or, as it is supposed to be, inuring them to lower tem peratures than those they have been accustomed to or have required in their native habitats, does not appear to be a possibility. It has been satis factorily determined that a plant must receive the same amount of heat for the proper perform ance of certain processes necessary to the pro duction of leaves, flowers and fruit, whether in places to which it is indigenous, or far removed therefrom in more northern latitudes The defi nite degree which it has demanded during certain epochs of growth is still required wherever it may grow; but the aggregate of heat may be re ceived during a shorter term in high latitudes be cause of the greatly increased length of the day, and the processes be hastened and maturity at tained at an earlier date. This is well illustrated in the growth of maize or Indian corn, which is said to be remarkably accommodating, though it must have a semi-tropical heat wherever grown, if only for a few weeks, and this heat it obtains even beyond the northern limits of the United States. It is well known that the varieties of maize grown near the northern limit of its cul tivation ripen earlier than those which are es teemed valuable further south. Man has applied to his purposes the property possessed by many plants of adapting themselves to the new con ditions, and the many varieties of maize, wheat, etc., attest the possibility of change within eer• tam limits. The principle above enunciated is, however, subject to sonic modifications as regards its application to certain physiological changes which have been observed to result from long continued efforts to cultivate plants under un natural conditions. Plants are, without doubt, capable of modification within certain limits. Witness the numberless varieties of grains and fruits, some of which appear to be more hardy than their progenitors. Many of these which ap pear to, or really do, thrive in more northern districts than those from which they were de rived, have merely acquired a greater suscepti bility to the influences of light and heat, and are thence aroused into earlier action, quickened in their vital functions, and mature under a lesser aggregate of heat as measured by the thermom eter, though for the critical periods of their ex istence they demand the same mean temperature as the original from which they were derived.
It is in the power of man to fix these peculiarities when observed, and in a measure to produce them by the selection of those which promise well, and continuing the selection with adequate care through several generations Vilmorin, by skillfully applying the principles which influence plants in their tendencies to sport into new va rieties and directing them into the desired chan nel, has almost created a new race of beets con taining twice as much sugar as their ancestors, and promising to be readily perpetuated. Ac climating the tender plants of the tropics, and inuring them to the cold seasons of the north or temperate latitudes, is, therefore, impossible, though some minor modifications upon those of short growth during the periods of fervid heat of the northern summer have been made. The olive and the orange have not been rendered more hardy, and the peach appears to be still en dowed with the same tenderness of bud it has always shown. The difficulties of acclimation may be illustrated by the fact that certain vege table products can be grown in particular lati tudes, while others, though they may attain con siderable size, can not be grown with any useful result. For instance, in England the vine will never yield grapes capable of making wine even of a quality equal to champagne; nor will to bacco ever acquire that peculiar principle which gives it, in the estimation of many, sogreat a value when grown in some other countries; and yet both the vine and the tobacco plant flourish in the soil of England. The botanist and the meteorologist can explain why this is so, and thus prevent the commencement of speculations which must end in loss and disappointment. It is of great importance to be able to define accu rately when a plant may be said to suit a particu lar climate. It is not enough that it live and send out leaves; it must be able to produce flowers and seeds and to elaborate the peculiar secretions and pro ducts on which its qualities depend. Indian hemp has grown in England, even, to the height of ten feet, with thick stems, vig orous leaves, and abundance of flow ers, birt it did not produce the resin matter upon which its supposed value as a medicinal.. agentdepends. The rhubarb of which, as regardii....' size and vigor of tliTt plant, thrives in England, does. notproduce a root of any medicinal value, or of the same quality as that grown in Chinese Tartary, from which, though known as Turkey rhubarb, it is de rived. The leaves. of the tea plant are harmless, or but slightly stimulating in certain latitudes, while they become narcotic and un wholesome in oth ers. This fact can be explained by the study of the con nection which ex ists between climate and vegetation a question to be solv ed by the botanist and meteorologist. It is science only that can explain the failure of attempts to cultivate the tea. plant in Madeira. and in the Indian Archipelago, while a variety of the Chi nese plant is now cultivated in the up per districts of In dia with great suc cess. In the United States we have so wide a range of lati tude and so fervent a. summer sun that many tropical plants, which mature in a single season, may be most success fully raised by means of some forcing in the spring, Witness the cultivation of the tomato and egg plant in high latitudes. These have been broken up into many varieties, some of winch ripen earlier than others, yet they are cer tainly killed with the same degree of cold in one situation as they are in another, and there is no reason to_ suppose that these or other plants will ever become acclimated so as to resist a greater degree of cold than would suffice to kill them in their native country.