Flowers and their friends

by Margaret Warner Morley

Sometimes there are several layers of skin cells where the plant needs a particularly thick skin; a in the illustration is an example of such a skin.

But it would not do to have an air-tight skin, even for a plant.

Our own skins are full of holes, or pores, as you know, to let out the extra water and other waste materials in what we call perspiration. The plants need such an arrangement as much as we do. So in their skin we find pores. You see the plant needs a great deal of water. The water is used in making the substance of the plant. It is also used in the sap to carry food about from place to place. Sap contains a great deal of water in order that it may flow easily. This water cannot all be used by the plant, and when it comes up from the roots in the sap a large part of it has to be got rid of by the leaves.

If the skin were solid, the water could not escape. But you know what protoplasm can do.

If the skin needs pores, it will make them. And this is how it does it.

If you peel off a bit of skin from the under side of a leaf and put it under the microscope, you will see something like this.

The round forms are the pores. The crooked lines between are the edges of the cell walls, and you are looking at them right through the outer wall of the skin, which is transparent like glass, otherwise you could not see the edges of the partitions.

Let us look at these pores, or stomata as we must call them, if we want to talk like botanists.

One of the stomata is called a “stoma”; stoma comes from the Greek and means a “mouth,” or “opening.” These little mouths, or stomata, are made of two cells lying close together. These cells reach through the skin into an open space back of it.