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Vertical section, dividing the embryo, a, caulicle: b, cotyledon; c, plumule. 3. Monocotyledons. These are more difficult. Perhaps it is not worth while to attempt to make the pupils see the embryo in Wheat and Oats. But the embryo of Indian Corn is larger and can be easily examined after long soaking. Removing the seed-covering, we find the greater part of the seed to be albumen.
The teacher's object now is to make the pupils understand the meaning of the answers they have given to these questions. In the first place, they should go over their answers and substitute the botanical terms they have just learned for the ones they have used. Morning-Glory. A seed covering. Some albumen. Two cotyledons. A caulicle. Sunflower. An outer covering. An inner covering. Two cotyledons.
A caulicle. The outer covering is the wall of the ovary, the inner the seed-coat. Bean. A seed covering. Two cotyledons. A caulicle. A plumule. Pea. The same as the Bean. They have also learned how the first leaves in the last three differ from those of the Morning-Glory, being considerably thicker in the Sunflower, and very much thicker in the Bean and Pea.
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.
If the way is thought out by even a single pupil the rest will be interested in seeing whether the plan will work successfully." I have been more successful in pricking the roots than in marking them with a brush. The caulicle can be proved by the manner of its growth to be of the nature of stem, not root. The main root grows from its naked end.
They have said that the caulicle was the part to grow first, and have spoken of the arched form of the young stem. Their attention should also be drawn to the root-hairs, which are well seen in Corn, Wheat, and Oats. They absorb the liquid food of the plants. A secondary office is to hold the seed firmly, so that the caulicle can enter the ground.
Closely applied to one side of this, so closely that it is difficult to separate it perfectly, is the single cotyledon. This completely surrounds the plumule and furnishes it with food from the albumen. There is a line down the middle, and, if we carefully bend back the edges of the cotyledon, it splits along this line, showing the plumule and caulicle within.
The cotyledons are very good illustrations of the different uses to which a single organ may be put, and the thorough understanding of it will prepare the pupils' minds for other metamorphoses, and for the theory that all the various parts of a plant are modified forms of a very few members. Nature of the Caulicle. Probably some of the pupils will have called the caulicle the root.
Again nothing. Yet both make for the nourishing spot. Theories are put forward, most learned theories, introducing capillary action, osmosis and cellular imbibition, to explain why the caulicle ascends and the radical descends. Shall physical or chemical forces explain why the animalcule digs into the hard clay? I bow profoundly, without understanding or even trying to understand.
Roots can also grow from the sides of the caulicle, as in Indian Corn. In this, it acts precisely as does the stem of a cutting. It can be prettily shown with the seedlings by breaking off a bean at the ground and putting the slip in water. It will throw out roots and the pupil will readily understand that the caulicle does the same thing.
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