No doubt every one knows the Lichens, the greenish gray growths, sometimes like rosettes or clusters of leaves or of fruit, on tree trunks or the gray rocks by the water, and even on the ground and old wood. Their forms are various and often graceful, and mingled with their greenish gray are many brighter colors, giving a rich tone to the rough surfaces they cover and adorn. But I dare say that most of us have thought of a Lichen as a single plant. It is not so, though it looks so exactly like one in its close union. It is a partnership, indeed; generally what looks like a single Lichen is a colony of partners keeping house together, or a manufacturing firm, if you like that expression of their business better. The partners are also kindred, or were so, in the past.

For there was a time long ago when there was only one big family of plants, the Algae; the brown Algae or seaweeds known as kelps often form the "wrack" or tangle of weeds like long leaves or branching stems, with berry or fruit-like bladders, thrown on the coast in great masses by a storm; and the red Algae, or the beautiful fern-like and coral like seaweeds that grow far down in the deep sea. There are also the green Algae, found in fresh water, or even on damp tree trunks and rocks. They have many odd forms. One kind, called a pond scum, is a frothy, slippery mass of spirally wound hands, floating in ponds or still water; another, called "green felt," is found in water also, and has egg like things from which spores or seedlike bodies escape to form new plants. They have filaments at the bottom, like roots, that are called "holdfasts." Lastly, there are blue-green Algae, jelly-like masses found on trees, rocks, damp earth or floating as green slimes in fresh water. Most water plants are active and independent.

They are on the upward road, for though they have not distinct stems, roots, leaves or fruit, their different parts, as I have already said, show a decided likeness to these, especially their "holdfasts" to roots and their air-bladders to fruit. The exquisite red seaweeds are as graceful in form and vivid in color as many flowers.

There is a remarkable foreshadowing of the moral law even among these early growths. Some have shirked their work, which was to absorb waste substances, and manufacture these into organized plant food. They tried to live on other growths, to the injury of the latter, and even sank to feeding on dead substances. They lost the green chlorophyll, which is necessary for manufacturing, though the red and brown Algae do not show its presence because their other coloring is more vivid. But it is present all the same with every busy, self-respecting plant. The lazy, pauper growths deteriorated more and more and at last were no longer Algae at all, but Fungi. They could not live by themselves; their only chance was to get active or well-stocked partners. As the Alga developed more and more into a likeness of a perfect plant, so the Fungus grew less like one. The white furry "mould" on bread or preserved fruit, the "mildew" on grapes and lilac leaves, the "black knot" of cherry and plum, the "ergot" of rye, the "rust" of wheat, do not look like plants unless you study them through a magnifying glass. Nor do the "slime moulds" or the mushrooms, toadstools, puff-balls and truffles bear much resemblance to flowers. Some of these, however, are both pretty and useful.

In the case of a Lichen the partners really seem to be of use to each other. The Fungus is not a mere pauper living on his more active kinsman. If you examine a Lichen you will find a large number of transparent threads, and in their meshes lie the green Algae, giving the whole a greenish tint.