The transition from the tropical rain forest to our own woodlands is one of the most interesting, as it is certainly the most gradual in nature. Lack of space prevents our stopping to note those strategic points along this pathway from a hot, steaming forest to the cool shade of our open woods, where traveling, in at least a virgin forest, may be done easily on horseback. As we come northward, and if we could travel continuously through the forest, we should lose first the epiphytes, then most of the lianes, and finally all the condition of vegetation crowding into every inch of space suitable for it. While trees in our virgin forests are as thick as they can be, the forest floor is open and on it grow only a few herbs that will stand lack of sunshine. But the really great difference is the long, unfavorable season in temperate regions where the forest must drop all its leaves, after, in at least our own Eastern States, the most gorgeous foliage coloring of any forest in the world. The winter months when the woody vegetation is practically fully exposed to the elements, are particularly severe in their effects. Leaf-fall, which is such a common sight as to arouse scarcely any interest, is the only device by which the great bulk of our forest trees survive, and only in the southern part of the region are there found such woody plants as the mountain laurel, rhododendron, American holly, and a few others which are evergreen but not cone-bearing ones, and are the only reminders of the truly evergreen forests of the tropics. The winter winds farther north and in the central treeless part of the United States prove too much for many kinds of trees, for instance, all the oaks and sassafras, none of which go very far north. There is sufficient rainfall to produce forests much farther north than they are found, but lower temperatures prevent trees from growing just as too little water stops their growth altogether. Toward the northern limits, or upon high mountains, the upper limits of the forest, we get the best idea of how persistent woody vegetation is in the general forest area of the eastern United States. Stunted, wind-swept and weather-beaten trees are often found only a couple of feet high and over sixty years old. Sometimes they will be flattened out on the ground or on bare rock, making great patches of bushy growth quite unlike their lofty relations in the lowlands. The growth rate for such plants is so slow that their annual rings are all but obscured. With such persistence in the production of these elfin forests, high up on mountains under the most unfavorable conditions, it is little wonder that below this are trackless woods, and that the northeastern United States has one of the finest developments of the temperate or summer forest in the world.