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?
[Illustration: FIG. 7.--Germination of Pea. _a_, caulicle; _b_,
cotyledons; _c_, plumule; _d_, roots.]
[Illustration: 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 assisted 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 illustration 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 associate 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 substitute the botanical terms they have
just learned for the ones they have used.