I have said that a maple seed is shaped like that of no other tree. I must describe here the seeds of the needle-leaved evergreens, which, though very much smaller, are somewhat like maple seeds in form. Go to a pine tree or a spruce, and get one of the cones that has begun to spread its scales apart. Shake the cone over a piece of paper. If nothing comes out from between the scales, cut or break the cone open with knife or hatchet. Under each scale will be found two seeds, each with a thin, one-sided wing. Spruces, hemlocks, firs, and arbor vitzs, all have this same type of seed, hid away in the same fashion, under the protecting scales of their cones. Do you understand how the wind, blow ing through the tops of evergreens, shakes the winged seeds from their places, and carries them far away? Do you understand why the ripe cones of these trees hang on so stubbornly, and spread their scales to allow the seeds to escape ? It is a peculiarity of the firs that they hold their cones erect. It would seem hard for the wind to get at the seeds, but the fir cones let their scales fall, and when they loosen, the seeds are freed.
Out of the balls of the sweet gum tree, which dangle on the twigs all winter, the wind shakes little winged seeds, not unlike those of the pines.
Do you know' the catalpa's long, green pods that hang all summer on the top of trees? They are longer than the newest lead pencil, and show no signs of splitting, until the autumn. Now, the two halves of the pod spread apart, and gradually the thin seeds shake out. Each one is in the centre of a thin, fringed wing, that looks as if made of tissue paper. The wind can carry these ghostly seeds for miles. Indeed, it is strange that they ever come to the ground, for they seem to have no thickness nor weight at all.
The birches all bear their seeds in cones, some long and pencil-like, others quite the shape of a pine cone. Under each quaintly notched scale
of the cone, a seed is borne; and each heart shaped seed has a thin rim, which acts like a wing, catching the wind as the seed falls. We shall look far in the woods before we find seeds daintier in form, or better sailors through the air, than those of all the birch family.
The hop hornbeam has a hop-like cluster of seeds, each in an inflated papery bag. When the leaves drop in the fall, the wind has a chance to pick off these little paper seed balloons, one at a time, from the clusters. Take off one of these little bags, open it, and you will find, set in the bottom, the shiny, pointed seed. It is likely to have a long journey, if there be a good breeze, before its bag is punctured.
Back to early May again, when the elm trees are green with their fruit clusters, before the leaves are fully out. Elm trees grow scattered through the woods, and no wonder : the seeds have papery rims, and the wind catches these little falling discs, and scatters them far from the tree where they were born.
The ailanthus tree, whose long, fern-like leaves make it look like a tree from the Tropics, is sowing its seeds all winter, with the help of the wind. Examine one. In the middle of a slim blade is the little seed. The blade is twisted as it ripens, and it sails through the air with a tilting, uncertain flight. After a look at a bunch of these seeds, and after throwing a hand ful of them out of an upper window, and watch ing them as they sail away, we shall understand how it is that ailanthus trees spring up in most unexpected places, year after year. And we shall bless the breeze that plants such trees along the hot pavements, and in the ugly back alleys of towns and cities, where few trees are able to grow at all.