One of the first things to attract the attention of botanist and layman alike when traveling through the Canadian Zone forests of the National Park are the great mass and variety of Lichens found growing on the trees, fallen logs, boulders and upon the ground itself. Two varieties are particularly abundant, the Goats Bear Moss, "Usnes", and air plant which hangs in festoons from the branches of the trees giving the forest a silver-gray color, and the common leathery Foliate Lichen especially common along the river bars and boulder filled valleys such as the Auto Camp at Longmire Springs. Here it grows with the mosses and other lichens and liverworts on the ground, covers boulders, and develops such masses of "Foliage" in the trees as to choke some of them to death.
All these lichens are of great interest scientifically because of their strange habit of associating with certain algae, to their mutual benefit. In fact a "lichen" is nothing more nor less than a combined fungus and alga, technically two separate plants but actually associated so intimately as to be one plant. The fungus plants which are the host of the alga, never grow alone. Without the food producing alga they cannot survive, but the same species of algae that usually grows with a certain fungi to form the lichens is occasionally found growing independent and alone. This is the proof that the lichen is made up of two, more or less, dependent plants.
Fungus plants contain no chlorophyll or green coloring matter which changes the raw food taken from the soil and air into soluable salts that can be assimilated by the plant. It is this digesting power that the algae contributes to the partnership. In return the fungi shelters the algae and supplies it with moisture and raw food from the soil. The algae is in reality the stomach of the lichen. Fungus plants that do not form this association, such as the mushrooms must depend upon other host plants for food that they have already digested and are always therefore parasitic plants.
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