_The Atlantic Forest._--The originally forest-covered eastern portion of North America, referred to under the term Atlantic forest, embraces the region from the eastern coast of the continent inland across the Appalachian Mountains and interior Continental basin to the eastern border of the prairies or plains; its southern limit, in a general way, is the coast-line of the Gulf of Mexico, but the arbitrary boundary, dividing it from the tropical forest, crosses the southern portion of Florida, and at the extreme southwest is drawn at the Rio Grande. The northern boundary of the Atlantic forest is also an arbitrary line, and follows the fiftieth parallel of latitude from the mouth of the St. Lawrence westward to the region about the Lake of the Woods; along this boundary the varied Atlantic forest merges with the monotonous and mostly coniferous subarctic forest. The region thus roughly outlined comprises over 2,000,000 square miles, and was at the time of the first coming of white men to America almost completely forest-covered, but the natural conditions are now profoundly modified, and to a great extent the trees have been cut or burned, and the land they shaded converted into cultivated fields. The Atlantic forest as a whole has two leading characteristics, the first being the great variety and frequently large size of the deciduous trees--that is, of broad-leaved trees, such as the oak, hickory, elm, maple, chestnut, etc., which drop their ripe leaves each fall and renew them the following spring--and the second, the intermingling of the trees of the class just mentioned with the coniferous trees, such as the pine, spruce, tamarack, etc., which have narrow, needle-shaped leaves and are usually designated as evergreens. While these general statements are sufficiently accurate for our present purpose, it is to be remembered that some of the broad-leaved trees (_Angiosperms_) are evergreen, especially in the southern portion of the Atlantic forest, as, for example, some of the oaks, the magnolias, the holly, etc.; while at the north, certain of the conifers (_Gymnosperms_) shed their leaves each fall, as is conspicuously illustrated by the yellow of the tamarack or larch forests of the northeastern portion of the United States and eastern Canada, in November, and the bright green of the same trees in May of each year. It is in the intermediate temperate region, between the mostly evergreen coniferous subarctic forests and the mostly evergreen broad-leaved trees of the Caribbean forest, that the wonderful transformation in the colours of the mountains and plains each autumn becomes the most conspicuous feature in the annual round of seasonal changes as expressed by the vegetation.