Plant Fertilization









You know if we stuck at home all the time and never got acquainted with other people, life would not only be dull but we'd be dull. And so it is, in a manner of speaking, with the people of the plant world, the tree peoples and all their relations of the woods and fields. This crossbreeding between flowers on different plants not only results in better seed and more hardy offspring, but creates new varieties. And as both these things, new varieties and vigorous growths, are evidently considered so important in the scheme of things, Nature, as a rule, takes precautions actually to compel the pistil of one plant to get the pollen necessary to awaken the little germ in its egg-case from some other plant.

In some kinds of flowers the pistil will absolutely refuse to open the door, as it were, should the pollen-grains from one of its own stamens come knocking; or, in plain English, will not produce seed when sprinkled with this home-grown pollen. In some flowers the stamens ripen before the pistil, in others the pistil ripens before the stamens. In either case, in order for fertilization to take place, the pollen must come from some other plant whose stamens have ripened earlier. Then, later, its own stamens, ripening, will have their pollen carried, by winged insects or the winds, to the pistils of other plants of the same species that have just ripened. Of course everybody knows that among trees and other plants of the very same species and in the same locality, the flowers don't all come out at once, but who would have thought that any of them meant to do this on purpose?

Another of Nature's precautions against "self-fertilization," i.e., the production of seed by a plant from its own pollen, is to grow one kind of flower having a pistil but no stamens and another with stamens but no pistil. In the Willows this thing is carried so far that the two kinds of flowers are on separate trees! In the flowers of the Catalpa, where each flower has its own stamens and its own pistil, the lobes of the stigma, the part of the pistil that catches and holds the pollen-grains, remain resolutely closed until after the stamens have ripened and their pollen has all been carried away by the bees.

THE GOLDEN FAIRY'S MAGIC TOUCH

But what takes place after the pollen comes to the pistil, as a result of the magic touch of those yellow pollen-grains, is the most wonderful thing of all; for it is in this way that every tree or flowering plant reproduces itself, after its kind. Very soon after the pollen-grain has fallen on the pistil, there grows from it a little tube which reaches down through the stem of the pistil (called the "style") into the egg-case (called the "ovary") at the bottom, where it unites with the egg-cell or germ, and together they form the seed which is to reproduce the plant.

In the Pine-cones the scales turn back and expose the inner surface at the time when the air is filled with the pollen from other Pines, which is thus able to act on the naked seed germs. Then the scales close up again and remain closed until the seeds ripen. Then they open again and let the seeds sail away on the winds to seek their fortunes in the great world of the forest.

WHY FLOWERS TALK GREEK AND LATIN

Among the advantages of scientific names for such important things as the parts of a flower are: (a) you know exactly what is meant; (b) one word saves nine--or more; (c) the scientific name is easy to remember when you get, from the dictionary, its original meaning; particularly when, as is so often the case, it is a "picture word."

Calyx (Greek for "husk"): The green "husk" of the flower.

Corolla (Latin for "garland"): What could better describe this crown of the "May queens," which all their petals together form?

Stamens (G. "thread"): The slender stems with the Anthers (G. "bloom") on the end, containing the Pollen (G. "dust").

Pistil: From L. for "pestle," the shape of which it resembles. Enlarged part, the Ovary (L. "egg"), contains the germ or "egg" to be fertilized by the pollen. The slender "handle" of the pistil is the Style (L. "stylus," the slender instrument the Romans used as a pen).

Stigma (G. "spot"): Not much of a picture-word, perhaps; but reflect that it is on this identical spot, and no other, that the pollen must fall. Remember, also, that it is usually moist or sticky, to hold the pollen; "stickma" is so close to the right word that you can hardly miss it!

HOW THE HICKORY-NUTS PUT ON THEIR JACKETS

There's simply no end to the interesting things to be learned about the flowering and seed-making business of the trees and their smaller relations of the plant world. So, of course, I couldn't attempt to tell them all here, but there's one I must speak of, even if we are nearly at the end of our chapter, and that is how the Hickory-Nuts put on their jackets, because we are all so interested in Hickory-Nuts in the autumn; and because it illustrates so well Nature's many thrifty ways in carrying on her own National Forest Service. Instead of going to the trouble and expense of getting new material to make the seed coat, the shell of the nut, she takes the inside of the germ case and turns it into the seed coat, right where it is!





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