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An hour or so ago I asked a little girl neighbor who spends a good deal of time with me exploring the wonderland of our back yard, to bring me a leaf from a young Ash that grows near the garage. And when she came back to my summer desk on the broad and breezy porch where we sit together so often and talk things over, "Oh!" said I, "that isn't a leaf!" "Isn't a leaf? I'd like to know why! I picked it from the Ash Tree, just as you told me to. Another of your jokes, I suppose." (In this little back-yard-and-front-porch private school of ours we don't consider "getting educated" is such solemn business as many people seem to think!) "Yes, it is a kind of a joke -- a way of putting it -- but it's true, all the same. This does look exactly like a leaf but it's only one-seventh of a leaf; only one-ninth, maybe. Would you mind trying again?" She was off like a shot, and pretty soon back she came with what she called "a little branch with seven leaves on it." You see had taken the hint -- like most young people, her wits are very nimble -- and, looking more carefully, had seen that the leaves of this species of Ash are arranged in groups of seven -- occasionally nine -- each group on its little "branch." The separate leaves in such cases are called "leaflets," and the whole group put together is the leaf. The "branch" to which the leaflets are attached is the midrib of the leaf, but each leaflet also has its own midrib and all the other parts of the ordinary simple leaf. These grouped citizens of Treeland are called "compound" leaves because they are compounded of many leaves. I do believe we could write a whole book -- this little girl and you and I -- just about leaves! Take the shapes alone. Not only is there the great variety which distinguishes different families of leaves from one another -- think of the elephant ears of the Catalapa, and then of the needles of the Pine -- but different species of the same family are sometimes so unlike that you'd never suppose they were any relation. Some Oaks, for example, are so "unoakish" in outline that you'd say, right off: "Why, this is no Oak at all!" But, by and by, you see the acorn come along. Then, of course, there can be no doubt about it. The leaves of the Chestnut-Oak look much more like the leaves of the Chestnut than they do like the leaves of the general run of Oaks; and if you want to tell the Ash from that of the Hickory before the nutting-season you'll have trouble, unless you remember that Ash leaves are always "opposite" on the midrib while on the Hickory they're "alternate."1 ("Opposite," in tree language, means just that-the simple leaves on a twig or the leaflets on the midrib of a compound leaf are exactly opposite each other; while "alternate" means that they are not opposite each other but are arranged at different heights, like the steps of a stairway.) On the other hand, the tree known as the Box-Elder has leaves so much like those of the Ash you'd never dream it was a Maple until you saw its seeds. THE WAYWARD WAY OF THE SASSAFRAS LEAVES Yes, and leaves right on the same tree sometimes differ so that you'd declare they came from different kinds of trees. From three different kinds of trees, even! Take the leaves of the Sassafras, for example. You'll find on the very same tree -- on the very same twig, often -- a three-lobed leaf, several oval leaves, and a leaf popularly known as the "mitten" because it's shaped, for all the world, like one of those big, clumsy, comfortable mittens that you'll be wearing pretty soon when you bring in wood for the kitchen stove on a cold winter's day. This playful habit of the Sassafras seems to be rather characteristic of the youth of the tree, for the mature trees' leaves are more nearly all of one pattern -- the lobed. To be sure, you could never find two leaves exactly alike; not even if you had before you, to select from, all the untold millions and billions and trillions of leaves from the days of the Garden of Eden up to the present. Yet the leaves differ more on some kinds of trees than others. The Sassafras and the Mulberry take the prize in this respect, I suppose, but there are others almost as inventive. Take the Burr-Oak, for instance. The outlines of its leaves wander around in all sorts of eccentric ways; but always somewhere -- usually about the middle -- are two deep indentations, as if some of the invisible little leaf tailors that work in the woods had tried to see how near they could come to cutting it in two without actually doing it; for these deep cuts are on opposite sides of the leaf and reach nearly to the midrib! Only a tough, leathery leaf like the Oak could stand a thing like that. And these same little tailors evidently know it; for; in cutting out the relatively thin leaf of the Sweet-Fern, where the cuts also reach nearly to the midrib, they alternate so that the two cuts never come opposite each other; it's a cut and a leaf, a cut and a leaf, right and left, all the way. |
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