IN PLANTS. The most obvious examples of ac elimatization are found in cultivated plants. While the original stock as well as the home of most cereals is not definitely known, it is be lieved that most of them have come from warm, temperate or semi-tropieal countries. They have now become fully acclimatized in far northern regions; indeed, some varieties of wheat, barley, etc., flourish even better in cold, temperate dis tricts than in their original home. The peach is believed to grow farther north now than in the days of the ancient Greeks. Evidences of ac climatization apart from man's influence are not wanting; for example. it has been shown that plants grown from seeds that mature at high altitudes are hardier than those grown from seeds that mature at low altitudes.
One of the most interesting results of acclima tization is the change of the plant periods. In Finland and northern Norway barley ripens in 89 days, while PM days are required in south ern Sweden. Varieties of corn which ripen in Ness' York in 93 days require 105 days in Texas. Interesting but not altogether harmonious re sults have been obtained from deciduous plants taken from temperate into tropical evergreen re gions. In most plants the leafless period is short ened, and in some eases (notoriously in the peach tree) it is eliminated altogether, the plant be coming an evergreen. Schimper has observed an other change, viz., the gradual loss of rhythmic growth; trees of temperate climes becoming in this respect more and snore similar to native tropical trees.
In some cases the capacity for acclimatization is incomplete, i.e., plants are unable to adjust all of their structures and functions to a new climate. This lack of adjustment is seen in some plants of warm regions which, when trans po•ted to cool regions, vegetate well hut fail to ripen wood. Many plants that can perform all their vegetative functions may still be un able to mature seeds; this is true not only of plants taken into cooler climates, but also in some eases of plants transported into warmer elimates. Some species occurring naturally in Spitzbergen are said never to ripen seed ; since their reproduction is now wholly vegetative, their original appearance in that region must necessarily have been at a period when the cli mate was much warmer than at present.
Darwin and others have discussed the influence of individual variation as compared with varia tion through offspring on the acclimatization of a species. There can he but little doubt of the gradual adaptation of a race through the nat ural selection of the hardiest individuals of each generation. Darwin also believed in the power of an individual to become acclimatized. The Wyoming experiment station reports that po tatoes from the same stock endure in the up lands frosts that would destroy them in the lowlands. This favors the idea of individual accli matization. Oranges, however, propagate hard ier forms by seeds than by grafts, whieli shows that gradual acclimatization through off spring may be more important. Northern-grown seeds are preferred by farmers, partly bemuse plants grown from them mature sooner than from home-grown seeds. In a few generations,
however, this hereditary peeuliarity is lost, and a new supply becomes necessary. it should be borne in mind that many of the above statements are based on imperfect observations, and that there is the greatest need for careful experiment in this field.
lry ANIMALS. The capacity of adapting them selves to changed environment is not possessed to the same degree by different species of one genus or by the individuals of any species. it varies with the hardihood. with the capacity for resistance, both of the individual and of the spe cies. Just what the changes are, whether chem ical or physical. that go on in the protoplasm of the body during the period of acclimatization, we do not. in many eases, know. 111 the acclima tization of fishes to denser media it is apparent that some solids are taken into the body, for the fishes sink when transferred again to fresh wa ter. Some organisms possess a remarkably high degree of acclimatization. Thus, few animals can resist a temperature of over 1 1 5° F., while 105° F. is the death-point of whole groups. Vet certain organisms live in hot springs in water of much higher temperature, although they may be similar in kind to, or even identical with. those that live in cooler waters outside, and probably were acclimated to the high tem perature by slow degrees as they made their way up the outlets into the springs. We know from experimentation that organisms can resist an amount of heat, of .tensity or of poison when accustomed to it by slow degrees, that would have been fatal had they been subjected to it suddenly. We owe the fact that certain domestic animals, such as the horse. cattle, clog, cat, fowls, rats, and mice, have spread with mankind over nearly all the world to the great capacity for acclimatization of these forms. most of which have originated ill warm climates. Likewise the ubiquity of such food plants as the potato and cereals, as well as cer tain weeds, is due to their great capacity of adap tation; for those plants and animal; that have a limited amount of adaptation have likewise a limited range of distribution. The quality and the strength of sonic animals seem actually to im prove in a new climate. Thus the merino sheep imported into Silesia and Pomerania from Spain seem to be superior in those lands to their Span ish ancestors, while the fleece of the Syrian sheep becomes finer in Spain; but in such cases it is diffieult to say just how much is dime to climate and how much to the breeder's skill and care. .l any of our domestic animals have been so long in the countries in Willa we now find them that we can never hope to know anything about the history of their importations; but the silkworm is comparatively so late an importation into Europe that We can follow its progress. It was brought from China first into holy, and now it is acclimated not only to southern France but even to the coast of the Baltic Sea, and it is able to live in some parts of the United States.