Flowers and their friends

by Margaret Warner Morley

This is not to call visitors to the flowers, but perhaps to keep them away. Where ants trouble the flowers, certain kinds have invented this very clever way of stopping the unwelcome visitors. They do not want the ants to take the honey from the flowers, so they secrete honey on the leaves or stems, and the ants take that instead of traveling on to the flowers.

Of course each living skin cell contains protoplasm. The protoplasm lies in a thin layer against the walls and builds, builds, builds, until the skin is thick enough.

When a good thick wall has been built, the protoplasm passes out through tiny openings in the inner wall into the inside cells, where it goes to work doing something else. The skin cells are then empty of protoplasm; they are only filled with air, and we say they are dead cells. Their hard walls are a good protection to the plant. In stems there is often a layer of thick cells behind the skin cells which also protects. These are called cork cells.

All very young plants have their stems covered with living skin.

Older plants, particularly woody ones, have their stems covered with the tough, dead skin. And trees have finally a thick layer of dead cork cells. In tree trunks the skin cells have disappeared entirely. The skin protected the young shoot; then its empty cells finally peeled off, as the cork cells formed underneath and made a thick bark. The bark then does the work of the skin. It protects the stem. It becomes very thick sometimes, as layers are constantly added beneath. The outside of the bark keeps peeling and scaling off.

Of course there are no stomata in bark. We find them only in the living skin. Bark does not need stomata, as it does not regulate the water supply. The young green parts of the plant do that by means of their covering of living skin. Living skin is usually transparent like glass.

It is tough and yet transparent. You see, the light must get through it to the cells which lie behind it.

There is usually no green color in skin. Sometimes there are other coloring materials, though not as a rule.

The living skin covers the leaf or stem or other part of the plant like a window of tough glass. Even where the skin is several cells thick, the light can pass through, just as it can through thick glass.