At the bottom of the blossom is a thick green oval body called the ovary, which afterwards becomes the seed-vessel. At the top, this narrows into a short column, surmounted by a three-cleft knob. Between the ovary and the gorgeously painted flower-leaves are six curious organs, termed stamens, consisting each of a long and rather slender stalk, and a head formed somewhat like a hammer.
If the green oval ovary in the centre is cut in two, it will be found divided into three chambers, in one or another of which, not usually in all, will be seen a row of little knobs or buttons attached to the partition in the middle. These little buttons are ovules, or seed-germs, and the special office of the ovary is to produce these germs, and to contain them until their full development and complete ripening into seeds. But if the knobs are left just as they are, unfertilized, they can never become seeds, and the plant will fail to reproduce its kind.
Turn we now to the stamens. Each of their hammer-like heads has two chambers, full of beautiful little grains which are called the pollen. Each grain is tastefully and delicately marked, and holds a transparent watery fluid, in which a number of extremely small solid particles are floating. What is required for the fertilization of the seed-germs is—that this fluid should be conveyed to and taken up by them. But they are in the centre of the thick green ovary—this in the chambers of the stamens!
A simple arrangement brings all about. At a certain time we may see the black heads of the stamens covered with a fine flour, which adheres to whatever touches them. This flour is made up solely of pollen-grains, escaping in unimaginable numbers from the chambers where they are produced. At the same time the knob which crowns the seed-vessel puts forth a thick and gummy ooze. The stamens are just long enough for their heads to rise a little above this knob, upon which the pollen, when escaping as I have stated, falls in great quantity, and is there held fast.
Each grain then begins to swell, and to sprout (as the Rev. J. G. Wood has it) something like potatoes in a cellar. All the sprouts, however, pierce the knob, and push downwards until they reach the seed-germs underneath. Each sprout is a tube of extreme minuteness, and when it reaches a germ, attaches itself thereto, and, through the channel so formed, the fluid is drawn out of the pollen-grain and absorbed by the embryo seed. Fertilization is thus effected, and the growth and development of the germ proceeds until it becomes a seed fully able, when planted, to reproduce a tulip.
Fern Spores.
In ferns, the spores ripen and are ready for dispersion and partial growth without any process of the kind. But, in truth, fertilization is as necessary to the continuance of ferns as to the perpetuation of other plants. The main difference lies in this: that the means of fertilization, and the real germs of new plants, are produced from the spores after they begin to grow.
When a spore falls upon a proper place for its development, a portion of the outer membrane begins to swell, and a tongue-shaped projection is formed, which becomes a sort of root. The one chamber of the spore gradually subdivides, and becomes two, four, and so on, until for the simple spore we have a tiny leaf-like expansion, now known as the prothallium, or representative of a leaf.