Do you remember the little balls and whip lashes in liver-worts, and the way in which the whip thrashed about in its bath cup and jumped to the ball? By the time plants grew into pines and palms and grasses, the whip lash turned to pollen grains, but the little ball remained much the same. It became an egg, packed away with others in a seed-case.
The egg always lies quietly in its case. Cut a ripe apple across the middle and see what a nice seed case it has. The egg has to stay where it is formed, and wait for the pollen to come to it. In the apple blossom there is a circle of pink petals. Those petals are not the flower at all. They are only the party dress the flower puts on for company. The real flower is in the center of the pink petals. In the very middle is a tiny white column, that swells out at the top into a spongy, moist button like a little dog's wet nose. This button often glistens as if it had a dew-drop on it. The column goes down to a knob hidden in a green cup, below the pink petals, and swelling out from the stem. In this knob are the eggs in a nest. By and by the pink petals will fall off, and the green knob will swell and grow and ripen into a juicy apple.
That is, it will do so if something happens in blossom time. The little column that rises from the seed case, and that has a spongy wet button on the tip, is hollow. It has a fairy tunnel in it. All around the column is a ring-around-a-rosy of little white hairs, with the yellow pollen grains on them. Those grains are so loosely set that a baby breeze fluttering the pink petals against them, or a blundering bee or butterfly in search of honey, brushes them off. Some of the pollen is sure to be brushed onto that little button in the middle when—down they go! The yellow dust sends a tiny rootlet on a toboggan slide down that tunnel, right into the eggs. When the two unite, they form a seed.
If that was all there was to it, it would be very simple. Every plant could make its own seeds, and wouldn't need any neighbors or relations to help it. But sometimes flowers have the eggs but no pollen. You can find a great many strawberry blossoms with the little button-topped column, but no yellow food for the eggs at the bottom of the tunnel. These imperfect flowers must always be planted among perfect flowered kinds of strawberries.
And sometimes, even when flowers have both of the seed making materials, they, cannot unite them. The egg wants pollen from some other plant. It doesn't want the help of its brother in making seed,
