Читать книгу Natural Wonders - Edwin Tenney Brewster - Страница 14

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Did you ever stop to think how extremely convenient it is to have two parents? Mama stays at home and takes care of the little children, reads and sings to them, tells them stories, puts them to bed, spanks them when they are naughty and kisses them when they are good. Indeed, you couldn’t get on very well without Mama. Neither could you get on very well without Daddy. Daddy doesn’t seem so important as Mama; but if Daddy didn’t go to work every day, and earn money for Mama and their little boys and girls, where would house and food and clothes and birthday parties and music lessons all come from?

Suppose there were no Mamas at all, but only just Daddies. Then of course there would be no aunties, nor nurses nor cooks nor big sisters nor kind ladies in the next house. There would be only just men; and half the men would have to stay home from the office to take care of the little boys of the other half, and then their work wouldn’t get done, and there would be no end of trouble.

It would be almost worse if there were only Mamas and no Daddies. For then all the Mamas would have to go out to work; and even when they could earn enough to hire a nurse, which I am afraid would not be often, the best of nurses isn’t like Mama. So it is really much better as it is, when we have both fathers and mothers, one to work abroad, and the other to work at home and take care of the children.

In fact, this arrangement is so much better than any other that pretty much all the living world has adopted it. You know the ears of corn which we buy in August and September and eat off the cob. You know too how it comes from the shop, all wrapped up in soft green husks, with the long silk hanging out of the end, that little girls in the country use for dolls’ hair, and ridiculous little boys try to smoke in pipes. The ear is the mother corn, and the kernels wrapped snugly away in the green husk are her children. Or rather they are her eggs, with the little corn plants inside, almost ready to be dried over winter and be planted and start life for themselves. Each kernel of corn has one fibre of silk, which is joined to it at one end and hanging out of the ear at the other.

The cob is the mother of the corn. Its father is the tassel.

The ear, then, is the mother of the corn. Its father is the tassel at the top of the stalk. From each branch of the tassel hang many tiny brown bags, each about as large as a grain of rice, and each filled with a very fine brown dust. This dust is called pollen. And unless a grain of this pollen falls on each thread of silk of each ear, then the kernel at the other end of the thread will never grow to full size and never become a seed; but will always remain small like the undersized kernels at the end of the ear. If the tassel is cut off; or the silk pulled out; or the ear tied up in a paper bag, then the ear forms no proper seed.

Sometimes, on an ear of sweet corn, one finds a few kernels, or a single kernel only, that instead of being white like the rest, is yellow. This means that somewhere in the neighborhood, it may be miles away, somebody has planted a field of common yellow corn, which we make into corn meal, but do not eat off the cob because it isn’t sweet. A grain or two of pollen from this yellow corn has been carried by the wind and fallen on the silk of an ear of sweet corn. So the father of that particular kernel is yellow and its mother white, and the kernel is colored just as if a white woman had married a Negro or an Indian.

Different plants manage these things differently. The ancient Egyptians, who lived on dates much as we live on corn and wheat, used to plant orchards of date palms as we plant orchards of our fruits. Every year, at the time when the cultivated date trees were in blossom, the Egyptian farmers used to go out into the desert, cut branches from certain wild palms which never bore fruit, and carry them in procession thru their date orchards. They did not know why they did this. They only knew that if they omitted the ceremony for a single year, that year they got no fruit. We know now, of course, that the date-bearing palm is the female tree; and the wild palm which doesn’t bear anything is the male. The procession with branches thru the orchards simply brought in the pollen.

Most plants, on the other hand, not to take any chances, have seed and pollen in the same flower. Many too, instead of relying on accident and the wind to carry one to the other, are arranged so that insects and humming-birds, in seeking food, shall make the transfer. Some, few, however, like the willows, have seed and pollen on separate trees.

Pollen Grains much enlarged.

The water plants manage in much the same way. They, for the most part, turn loose in the water what in them corresponds to the pollen, and waves and currents carry it to the young seeds. The simpler water animals, sponges and sea-anemones and shell-fish do much the same. While the female sea-urchin or star-fish produces eggs as small as dust, the male produces a still finer pollen-dust, which we call milt or sperm. If one grain of this happens to float against an egg, the egg at once begins to change to a young animal. Otherwise after a week or so the egg dies and that is the end of it. Of course, under these conditions, the chance of egg and milt getting together is pretty slim, and the waste of eggs is enormous. So the fishes, which can move about, have a much better plan. When the female salmon, for example, swims up the rivers to leave her eggs among the gravels in the swift water, the male goes along with her. After she has laid her eggs and gone away, along comes her mate and scatters milt over them. So the salmon egg is pretty sure to grow; and the salmon can afford to have few eggs and larger, and so give her little ones more yolk to live on and a better start in the world.

The bees have a still better device. The single queen bee, as everybody is supposed to know, lays all the eggs of the hive. When the queen is young and the new swarm is just starting, she annexes enough of this pollen-milt-sperm to last her the rest of her life, and stores it up in a little sack. Then whenever she lays an egg, all she has to do is to give this sack a squeeze, press out a little of the contents, and start the egg growing into a new bee.

Strangely enough, however, altho this practice of having two parents is so very common among both animals and plants, and so universal among human beings, it is not, so far as we can see, at all necessary. Potatoes are thick underground branches, and not seeds at all. Yet we plant them and they answer exactly as well. Many lowly creatures, like the yeasts, the bacteria, the infusorians of stagnant water, and the like, never have anything resembling seeds or eggs. There is a parent. The parent splits in halves. There are two children. And where is the parent?

Among the common green plant-lice which swarm on the leaves in the summer, the males all die early in the season. After that the females go on laying eggs, and these hatch more females which lay more eggs, for ten and twelve generations, before the cold weather comes on and some of the eggs begin to hatch out males once more. They get along exactly as well when each insect has only one parent, as when it has two.

In the case of the queen bee, if while the egg is being laid she squeezes the sack, then the egg hatches out a worker, which has therefore, two parents. But if she does not, then the egg hatches out a drone, which has only one. There are many other strange facts of this sort, which have been known for a long time, but which nobody has yet been able quite to understand.

Some facts still stranger have recently come to light. It has found that in the case of many sea creatures, star-fish, sea-urchins, shell-fish and others, that if the eggs are kept in common sea water, but kept carefully away from any milt, they soon die, and never grow up at all. But if any one of a considerable number of substances is added to the water, sugar, salt, acids, and other things, then the eggs, tho they still have only one parent, proceed to grow into the proper sort of little sea creatures, just as if they had two.

It is really a great mystery; the most that any one can say is that the eggs are there, but something in the water, or the absence of something, stops their growing. Add sugar, salt, acid, or milt and they grow. In the case of the land animals, this something is probably in the blood—for as you know, the blood is salt like the sea, and in many other ways much like it.

At any rate, this is practically a most convenient arrangement. A mother bird, for example, is herself born with all the eggs she is ever going to lay already formed inside her. But something in her blood keeps those eggs from growing bigger than pin heads. They don’t grow into proper eggs, that can hatch into little birds, until the mother bird gets a mate to help her build the nest, and to feed the little birds when they come, and sometimes to feed her too. Then some of them do grow up and hatch; and the two old birds take care of them.

But as I said, it is all a very great mystery, which the wisest men do not yet completely understand, and little boys and girls can hardly expect to understand at all.