You may want to begin by looking at a rough diagram of the parts of a flower--any of these images may help. Do your students already know the names of the parts? Even better: find some real flowers of this type to examine.
We have now seen how a plant springs up, feeds itself, grows, stores up food, withers, and dies; but we have said nothing yet about its beautiful flowers or how it forms its seeds.
If we look down close to the bottom of the leaves in a primrose root in spring-time, we shall always find three or four little green buds nestling in among the leaves, and day by day we may see the stalk of these buds lengthening till they reach up into the open sunshine, and then the flower opens and shows its beautiful pale-yellow crown.
We all know that seeds are formed in the flower, and that the seeds are necessary to grow into new plants. But do we know the history of how they are formed, or what is the use of the different parts of the bud? Let us examine them all, and then I think you will agree with me that this is not the least wonderful part of the plant.
Remember that the seed is the one important thing and then notice how the flower protects it. First, look at the outside green covering, which we call the calyx. See how closely it fits in the bud, so that no insect can creep in to gnaw the flower, nor any harm come to it from cold or blight.
Then, when the calyx opens, notice that the yellow leaves which form the crown or corolla (ignore the Toyota, scroll down to the plant version), are each placed alternately with one of the calyx leaves, so that anything which got past the first covering would be stopped by the second.
Lastly, when the delicate corolla has opened out, look at those curious yellow bags just at the top of the tube (top flower on the right). What is their use?
But I fancy I see two or three little questioning faces which seem to say, "I see no yellow bags at the top of the tube."
Well, I cannot tell whether you can or not in the specimen you have in your hand; for one of the most curious things about primrose flowers is, that some of them have these yellow bags at the top of the tube and some of them hidden down right in the middle. (Fantastic photos here) (Note to teacher: if you are examining some other kind of flower--since we don't have English primroses here--this will probably not apply. Primroses are a distylous species; others are named here.)
But this I can tell you: those of you who have got no yellow bags at the top will have a round knob there (see the flower on the left), and will find the yellow bags buried in the tube. Those, on the other hand, who have the yellow bags at the top will find the knob half way down the tube.
Now for the use of these yellow bags, which are called the anthers of the stamens, the stalk on which they grow being called the filament or thread. If you can manage to split them open you will find that they have a yellow powder in them, called pollen, the same as the powder which sticks to your nose when you put it into a lily; and if you look with a magnifying glass at the little green knob in the centre of the flower, you will probably see some of this yellow dust sticking on it. We will leave it there for a time.Students to narrate at this point.
Now we will examine the body called the pistil, to which the knob belongs.
Pull off the yellow corolla (which will come off quite easily), and turn back the green leaves. You will then see that the knob stands on the top of a column, and at the bottom of this column there is a round ball, which is a vessel for holding the seeds. In the middle of the ball, in a cluster, there are a number of round transparent little bodies, looking something like round green orange-cells full of juice. They are really cells full of protoplasm, with one little dark spot in each of them, which by-and-by is to make our little plantlet that we found in the seed. (Do they look a bit like the inside of a cucumber?)
"These, then, are seeds," you will say. Not yet; they are only ovules, or little bodies which may become seeds. If they are left as they are they would all wither and die. But those little grains of pollen, which we saw sticking to the knob at the top, are coming down to help them. As soon as these yellow grains touch the sticky knob or stigma, as it is called, they throw out tubes, which grow down the column until they reach the ovules. In each one of these they find a tiny hole, and into this they creep, and then they pour into the ovule all the protoplasm from the pollen grain which is sticking above, and this enables it to grow into a real seed, with a tiny plantlet inside. This is how the plant forms its seed to bring up new little ones next year, while the leaves and the roots are at work preparing the necessary food.
Think sometimes when you walk in the woods, how hard at work the little plants and big trees are all around you. You breathe in the nice fresh oxygen they have been throwing out, and little think that it is they who are making the country so fresh and pleasant, and that while they look as if they were doing nothing but enjoying the bright sunshine, they are really fulfilling their part in the world by the help of this sunshine; earning their food from the ground; working it up; turning their leaves where they can best get light (and in this it is chiefly the violet sun-waves that help them), growing even at night, by making new cells out of the food they have taken in the day; storing up for the winter; putting out their flowers and making their seeds, and all the while smiling so pleasantly in quiet nooks and sunny dells that it makes us glad to see them.