英文科學(xué)讀本 第三冊(cè)·Lesson 54 Seedlings

Lesson 54 Seedlings

Can you tell me, Fred, all about the way the little seed germ grows till it becomes a plant, able to take care of itself? asked Norah. "I learned so many new things from what you told me about the seeds, that I should so much like to know just how that little germ grows."

Well, I think I can tell you something about it, said Fred, "for that was our lesson this morning."

You know that every seed contains in itself the germ of a little plant, with root, stem, leaves, only waiting for an opportunity to grow. Teacher showed us some peas which he was growing in flowerpots; some were only just starting, others were quite little plants with leaves.

After the seeds have been in the damp soil for some time the first effect of the moisture is to cause the testa to swell up and wrinkle till at last it bursts. While this has been going on, the warmth and moisture together have made the tiny germ wake up, as it were, from its long sleep and begin to stretch itself out. It happens, you see, that the testa splits just at the time when the germ has woke up, is beginning to grow, and wants more room.

The two parts of the germ grow—the radicle forcing its way down into the soil, the plumule upwards towards the surface, for light and air.

But I can't see how these little germs can grow, said Norah. "Where do they get their food? It must be some time before the little root can grow enough to make its way into the soil, and then I think you told me that the root-hairs, which feed the plant, don't come for some time. I can't see how the little thing is to get any earth-food, and it certainly can't get any air-food, for there are no leaves—no parts of it above the ground."

Well, said Fred, "I am not surprised to see you puzzled about this, Norah. But you may be sure everything is well arranged, although it is very wonderful. Those seed-leaves are simply a storehouse of food for the little germ, with just the proper kind of food, and just the proper quantity, to feed it till it can grow root-hairs to absorb earth-food from the soil, and leaves to breathe in air-food from the air."

As soon as this is the case the seed-leaves wither and drop off.

SUMMARY

When the seed is put into the ground, the outside skin swells and bursts, the germ wakes up, and commences to grow—the plumule making its way upwards, the radicle pushing itself down into the soil. The seed-leaves feed it as it is growing, till the root can take up food from the soil.