SECOND READING.
Although the flower and its fruit tell us what the plant is, and leaves do not with any certainty, there is yet a strong similarity, as well in texture as in shape, in the leaves of most of the plants comprised within any one family. Especially in texture is this marked similarity observable; and, perhaps, in most cases the peculiar structure of the leaf, aside from its shape, is indicative of the order to which the plant belongs. The leaves of the grasses are very much alike; so are the leaves of the sedges;—and though it is true, also, that in some instances a sedge-leaf might be mistaken for a grass-leaf, it must be remembered that the sedge family and the grass family have some points of similarity.
Again, if we should come upon a plant belonging to the common potato or nightshade family, we should be almost sure to recognize the family resemblance at the very first glance, provided we were already familiar with a number of plants included in that order. Yet the leaves of the nightshade family vary considerably in shape, and it is therefore decisively the texture and peculiar appearance of the leaves, that announce the kinship of the plant. And thus we are led back to the consideration of the willow-oak and chestnut-oak leaves, which, entirely unlike the typical oak-leaf in shape, are yet very much like all other oak leaves in texture and other essential structure.
Leaf of the Rose.
Still more widely divided than oak leaves, are such as are called pinnate, in which the separated parts are actually distinct leaflets, some even provided with stalks. Such compound leaves may be seen in almost every garden by looking at a rose-bush. In the cut, we see what appears to be five distinct leaves attached to one twig; but the fact is that they are only leaflets, and, together with the stalk which bears them all, constitute but one complete leaf. Each of these leaflets has a short stalk, connecting it with the main stem, which passes between the pairs, and has an odd leaflet at the end. A rose-bush may have leaves of seven or nine leaflets.
Among our forest trees, hickory, walnut, butternut, locust, and ash have pinnate leaves; and on the honey-locust not only are the leaves pinnate, but on the same tree, may also be found leaves doubly pinnate, and even tripinnate. Compound leaves may be seen also in the pea-vine, which is simply pinnate; but here the place of the absent terminal leaflet is supplied by a tendril.
But if we examine a bean-plant, we do find an odd leaf, together with a pair of leaflets; that is, each leaf is composed of three leaflets. The many varieties of bean-plants are all thus three-leaved. Besides, the woods are full of three-leaved plants, belonging to other kinds of the bean or pulse order of plants. In addition to these and some others, we must not overlook a most extraordinary three-leaved plant, plentiful in almost every forest, and on almost every stone-fence in the country; only too well known by persons who have been poisoned by it, and yet not so well known by most people as it ought to be, for it is often confounded with a plant having digitate leaves.
Leaf of Poison-Vine.