Outlines of Lessons in Botany Part 2

How many leaves are there at each joint of stem after the first pair?

How do they differ from the first pair?

SUNFLOWER OR SQUASH.

What are the parts of the seed?

What is there in the Morning-Glory seed that this has not?

How do the first leaves change as the seedling grows?

BEAN.

What are the parts of the seed?

How does this differ from the Morning-Glory seed?

How from the Sunflower seed?

How do the first pair of leaves of the Bean change as they grow?

How many leaves are there at each joint of stem?[1]

[Footnote 1: There are two simple leaves at the next node to the cotyledons; after these there is one compound leaf at each node.]

How do they differ from the first pair?

PEA.

What are the parts of the seed? Compare it with the Morning-Glory, Sunflower, and Bean.

How does it differ in its growth from the Bean?

What have all these four seeds in common?

[Ill.u.s.tration: FIG. 7.--Germination of Pea. _a_, caulicle; _b_, cotyledons; _c_, plumule; _d_, roots.]

[Ill.u.s.tration: FIG. 8.--Germination of Bean.]

What has the Morning-Glory seed that the others have not?

What have the Bean and Pea that the Morning-Glory has not?

How does the Pea differ from all the others in its growth?

What part grows first in all these seeds?

From which part do the roots grow?

What peculiarity do you notice in the way they come up out of the ground?[1]

[Footnote 1: This question refers to the arched form in which they come up. In this way the tender, growing apex is not rubbed.]

The teacher must remember that, unless the pupils have had some previous training, they will first have to learn to use their eyes, and for this they will need much judicious help. They should be a.s.sisted to see what is before them, not told what is there. It is absolutely necessary that these questions should be thoroughly understood and correctly answered before any conclusions are drawn from them. For this purpose abundant material is indispensable. It is better not to attempt these lessons on seeds at all, unless there is material enough for personal observation by all the pupils.

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;[1] 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_.

[Footnote 1: The term radicle is still in general use. The derivation (little root) makes it undesirable. Dr. Gray has adopted caulicle (little stem) in the latest edition of his text-book, which I have followed. Other writers use the term hypocotyl, meaning under the cotyledons.]

I consider this the best order to study the seeds because in the Morning-Glory the cotyledons are plainly leaves in the seed; and in the Squash or Sunflower[2] the whole process is plainly to be seen whereby a thick body, most unlike a leaf, becomes an ordinary green leaf with veins.[3] In the Sunflower the true leaves are nearly the same shape as the cotyledons, so that this is an especially good ill.u.s.tration for the purpose. Thus, without any hint from me, my pupils often write of the Bean, "it has two thick leaves and two thin leaves." In this way the Bean and Pea present no difficulty. The cotyledons in the first make apparently an unsuccessful effort to become leaves, which the second give up altogether.

[Footnote 2: The large Russian Sunflower is the best for the purpose.]

[Footnote 3: These lessons are intended, as has been said, for children over twelve years of age. If they are adapted for younger ones, it is especially important to begin with a seed where the leaf-like character of the cotyledons is evident, or becomes so. Maple is excellent for the purpose. Morning-Glory is too small. Squash will answer very well. I think it characteristic of the minds of little children to a.s.sociate a term with the first specimen to which it is applied. If the term cotyledon be given them first for those of the Bean and Pea they will say when they come to the Morning-Glory, "but those are _leaves_, not cotyledons. Cotyledons are large and round." It will be very difficult to make them understand that cotyledons are the first seed-leaves, and they will feel as if it were a forced connection, and one that they cannot see for themselves.]

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 subst.i.tute the botanical terms they have just learned for the ones they have used.

COMPARISON OF THE PARTS OF THE SOAKED SEEDS.

_Morning-Glory_. A seed covering. Some alb.u.men. Two cotyledons. A caulicle.

_Sunflower_. An outer covering.[1] An inner covering. Two cotyledons. A caulicle.[2]

[Footnote 1: The so-called seed of Sunflower is really a fruit. The outer covering is the wall of the ovary, the inner the seed-coat. Such closed, one-seeded fruits are called akenes.]

[Footnote 2: The plumule is sometimes visible in the embryo of the Sunflower.]

_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. Why should the Morning-Glory have this jelly that the others have not? Why do the first leaves of the Sunflower change so much as the seedling grows? What becomes of their substance? Why do those of the Bean shrivel and finally drop off? By this time some bright pupil will have discovered that the baby-plant needs food and that this is stored around it in the Morning-Glory, and in the leaves themselves in the others. It is nourished upon this prepared food, until it has roots and leaves and can make its own living. The food of the Morning-Glory is called _alb.u.men_; it does not differ from the others in kind, but only in its manner of storage.[1]

[Footnote 1: Reader in Botany. III. Seed-Food.]

Also the questions have brought out the fact that the Bean and Pea have the plumule ready formed in the seed, while the Morning-Glory and Sunflower have not. Why should this be? It is because there is so much food stored in the first two that the plumule can develop before a root is formed, while in the others there is only nourishment sufficient to enable the plantlet to form its roots. These must make the second leaves by their own labor.

3. _Comparison with other Dicotyledons_.--The pupils should now have other seeds to compare with these four. Let them arrange Flax, Four o-clock, Horsechestnut, Almond, Nasturtium, Maple-seeds, etc., under two heads.

_Seeds with the Food stored _Seeds with the Food stored outside the plantlet in the embryo itself (Alb.u.minous)_. (Exalb.u.minous)_.

Flax. Four-o'clock. Acorn. Horsechestnut. Almond.

Morning-Glory. Maple. Sunflower. Squash.

Bean. Pea. Nasturtium.