There are many seeds which would be good to begin work on, any kind would be interesting, but it is best to use some nice big ones which allow us to see the parts easily. Good ones to choose would be broad beans or peas. Notice first the size and shape of the dry seed of the bean, make a drawing of it, and then place it in water. After a few hours you will see that the outside skin wrinkles up; this is because the skin absorbs water and increases in size, and so becomes too big for the rest of the seed (see fig. 3, A, B). After the water has soaked right into the substance of the seed you will find that the outer skin fits again and is once more smooth, and that the whole seed is larger than it was before it was soaked (see fig. 3, C).
Fig. 3. A single Bean seed, A dry; B half soaked, when the skin wrinkles; C fully soaked and swollen.
Take one of these soaked beans and examine its structure. Notice the black mark where it was attached to the parent pod, and the little triangular ridge pointing towards it (see fig. 4, A). Now carefully peel off the skin, noticing that there are two skins, an outer thick one and an inner thin one, which protect the parts within. When you have removed the skin, you will find that the inner portions of the seed split very readily into two thick fleshy parts, and that lying between them is a tiny young plant. Notice how this young plant is connected on either side with the fleshy parts, so that to separate them you must tear one side or the other as in fig. 4 B, where at (a) we see the scar left where the tiny plant (p) was torn from the side. The two big fleshy parts are really portions of the young plant, and are in fact its two first leaves, but they are very different from ordinary leaves, and are packed with food substances, and are called the cotyledons, or “nurse-leaves.” Notice also the tiny root of the baby plant or embryo, as it is called; it bends a little to the outer side, and fits into a kind of pocket in the skin of the coat. You can see the shape of the root even from the outside of the dry bean (see fig. 4, A (r)). You will find in the pea, cucumber, and many other seeds, that there is also the tiny embryo with its two nurse leaves, the whole being protected by strong coats. The differences between the bean, pea, and cucumber seeds are only in the details of shape and colour, not in the actual parts of the seed.
Fig. 4. A, outside of Bean; (h) black scar showing where the bean was attached to the pod; (r) ridge made by young root; B, bean split open; (n) nurse leaves; (p) baby plant; (a) scar where the baby plant was separated from the nurse leaf on that side.
In the case of maize and corn, however, you will find that the seed does not split into two equal parts like the bean, but that the young plant lies at one side of the seed, and a solid white mass fills the rest of the space (see fig. 5). There are also differences in the seedlings which you will notice when they begin to grow.