IX. Plants Have Visitors and Travel AbroadEdit
What a great thing it is for little boys and girls to have play mates. How many more things you learn to know and to do, and how much better a time you have, if you play with others. It is best of all to have some one who has lived in a very different place, and in a very different way from yourself, to play with.
Do you live in the country? And have you some little cousins who live in a city ? Very likely they visit you in the summer. What a treat it is to them. A farm is a strange, delightful land to a city boy. How many wonders he sees, and how eager you are to explain them to him. Then you go to the city to visit, and you see enough new things to talk about for weeks. It is a good thing to go away from home, and to have visitors. Moving about and mixing with people brightens us all wonderfully, and makes us change some of our ways of thinking and living.
It is just the same with plants. Plants that live by themselves, and do everything for themselves, are like hermits in caves. The liver-worts, mosses and ferns are sort of hermit plants. Palms and pines and grasses travel a little. Their pollen grains take journeys on the wind, and visit other plants. They begin to change then. There are thousands of varieties of the higher plants. As plants cannot run about to make new acquaintances, like little boys and girls, they need messenger boys to carry letters. They use the wind, the bees, the butterflies and the birds. By these winged messengers they exchange gifts with their friends and neighbors and relatives in distant fields, just as we exchange gifts at Christmas. Let us see just how they do it.
You have often noticed the grains of yellow powder on little upright threads in the hearts of flowers, haven't you? They are very plain in roses, in the blossoms of fruit trees and buttercups, and many common flowers. Perhaps some one has brushed a buttercup under your chin to see if you like butter. If you do that yellow dust rubs off on your chin. It is so loosely fastened, in some flowers, that you can blow it off. That yellow dust is pollen. Pollen is one of the things the plant needs to make seed. The other thing is an egg.
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, but of its cousin. A Bartlett pear wants pollen from another variety of pear altogether. Fruit growers know this and plant different kinds of pear trees in an orchard. If not too distant, the pollen will find the eggs that need it.
So, in blossom time, there is a great deal of blowing about and visiting and exchanging of gifts between flowers. They seem to be amusing themselves; tossing their pretty locks, swinging their silken petticoats in the breeze, and gossiping with bees and butterflies about what is going on in neighboring fields and orchards. One can fancy a little sugar pear tree saying to a bumble bee: "Put some of my nice yellow pollen on your legs and take it over to Mrs. Bartlett, with my compliments. I'm sure it's what she needs for her little seed babies. Just press the button and she'll do the rest."
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From the tassels at the top of the stalk the pollen falls on the silk at the end of the ears which are sprouting below.
Isn't that friendly? The plant world is very busy and helpful when it seems to be playing. The tall, plumy tassels at the tops of corn stalks, swing much as you do under the maple tree. But those tassels are so loaded with pollen that you can often see a brown dust hovering over a corn field. As the wind blows the tassels, the pollen is shaken down in clouds. It falls on the corn silks below. Each one of those silks goes back to little eggs on the baby cob. A pollen grain must fall on the hollow tip of each silk, and slide a hair root down the long tube to the egg, or there would be no kernels, or seeds, on the ear of corn.
The wind is the only messenger of the pines and palms, the grasses and grains, and many of the straight-veined plants. The lilies and other bulb plants of the straight-veined family, have bee and insect visitors. Nearly all of the net-veined plants have such sweet blossoms and fruits that bees and butterflies visit them. When fruits and seeds are ripe the winds blow them abroad, the birds eat them, fly far away, north and south, sometimes hundreds of miles, and plant the seeds in other countries. In this way plants were scattered long before men began to grow them for food. The soil and rain and sunshine were not always the same, so plants had to change. Many varieties of palms and pines, grasses and wild fruits were made. The plants that traveled and had the greatest number of visitors, changed the most.