Some plants have their stalks made strong in a singular way. There is a flinty earth in them. This is the case with wheat, and rye, and most kinds of grass. See how tall the stalk of rye or wheat is. And it is very slender. But as the wind bends it over it does not break, because the flint in it makes it so strong.
It is this flint in different kinds of straws that fits them to be used in making hats and bonnets. They would not be firm enough for this use if there was no flint in them.
You can not see or feel the flint in the straw. The reason is, that the particles of the flint are so fine, and are so well mixed up with the fibres or threads of the straw. It is this fine flint in straw that makes its ashes so useful in polishing marble. In some plants you can feel the roughness that is made by the flint. You can feel it in the scouring-rush, which is sometimes used by house-keepers in scouring. In this there is more of the stony substance than there is in the straw of your hat, and it is not as fine.
How flint gets into stalks.
But you will ask how stone or flint gets into these plants. It is sucked up from the ground by the mouths in the roots, and it goes up in the sap to where it is wanted. It is wanted in the stalk of the grain, and so it stops there. It never makes a mistake by going into the kernels of the grain. If it did, the flour that is made from them would be gritty, as we should find out when we came to eat the bread.
Shrubs.
All plants that have no wood in their stalks die down to the ground in the autumn, though the roots of some of them live through the winter. But trees, you know, remain from year to year. So do shrubs and bushes. These may be considered as little trees. Some shrubs are so small that they do not need to have their stalks woody merely to support the branches. Thus the currant-bush could have its branches well supported if the stalks were not woody. In such cases the stalks are made woody so that they may last over the winter.
Vines.
Stalks and trunks commonly stand up of themselves. But there are some that can not. When this is so we call the plant a vine. Vines are supported in various ways. Some are held up by merely winding around something. This is true of the bean-vine. It winds itself, as it grows, around the pole that is put up for it. The hop-vine is supported in the same way. It is, you know, quite rough, and so it can cling firmly even to quite a smooth pole.
Tendrils.