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After this preliminary work has been done, the names of the parts can be given to the pupils. They may be written under each drawing thus, A=Caulicle; B=Cotyledons; C=Roots; D=Plumule. The whole plantlet in the seed is the embryo or germ, whence the sprouting of seeds is called germination. Dr.
Imagine the tiny primrose plantlet to be made up of cells filled with active living protoplasm, which drinks in starch and other food from the seed-leaves. In this way each cell will grow too full for its skin, and then the protoplasm divides into two parts and builds up a wall between them, and so one cell becomes two.
For reasons hereafter given, I consider the Morning-Glory the best seedling to begin upon. Having a series, as above described, before them, the pupils should draw the seedlings. When the drawings are made, let them letter alike the corresponding parts, beginning with the plantlet in the seed, and using new letters when a new part is developed.
Yet in this tiny plantlet lies hid the life of the future plant. When a seed falls into the ground, so long as the earth is cold and dry, it lies like a person in a trance, as if it were dead; but as soon as the warm, damp spring comes, and the busy little sun-waves pierce down into the earth, they wake up the plantlet and make it bestir itself.
One of these halves will have a small dent at the pointed end, while in the other half you will see a little lump, which fitted into the dent when the two halves were joined. If you look carefully, you will see two little points at this end, which are the tips of future leaves. Only think how minute this plantlet must be in a primrose, where the whole seed is scarcely larger than a grain of sand!
Often there may be several branches upon the stem, and each of these may be used as a new plantlet provided it has some roots or a rooted part of the main stem attached to it. By this method I have obtained nearly 100 rooted plants from a single specimen of Holt's Mammoth sage grown in a greenhouse. And from the same plant at the same time I have taken more than 100 cuttings.
Sometimes the seed-leaves themselves come above the ground, as in the mustard-plant, and sometimes they are left empty behind, while the plantlet shoots through them. And now the plant can no longer afford to be idle and live on prepared food. It must work for itself.
It drinks in the sunshine, and with the warmth of it, and to the glory of its own life, it blossoms. It has come from a tiny helpless seed to a living plantlet with the smallest stem and root, and while the stem fights for a place in the air the root never ceases to get a strong hold of the dear earth in which the plant finds its home.
But these new particles cannot come in at the roots, for the seed has none; nor through the leaves, for they have not yet grown up; and so the plantlet begins by helping itself to the store of food laid up in the thick seed-leaves in which it is buried.
We think the use of the hole is to let out the milk; but the nut knows that its real object is to let out the seedling. The knob grows out at last into the young plantlet, and it is by means of the soft hole that it makes its escape through the shell to the air and the sunshine which it seeks without. This brings us really down at last to the true raison d'être for the milk in the coco-nut.
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