no two trees are exactly alike. There are specific as well as generic differences which are strongly marked. One tree leads a rugged, wild, and struggling life; another an easy, luxurious life. The rough and fuzzy leaf of the slippery elm, the silky leaf of the beech, the shiny leaf of the gray birch, these are all widely different; but there are also distinct differences between the leaves of the several kinds of birches, elms, and maples.
Still, there are puzzling similarities, and one is often compelled to study minute details in order to make sure of a particular species. The catalpa leaf is mentioned as that having the simplest form. It is without divisions, and has an entire and unbroken edge. The magnolia leaf, which is oval, might as well have been
taken as the type; and there are others equally simple. The most complex form of leaf is exemplified in that of the horse-chestnut.
A very interesting exercise may he had in tracing the differences in the shapes of the leaves of trees of the same family,