Home › Volumes › Mosses and Lichens › Herbarium

The Method by Which Peat-mosses Encroach Upon Water to Form Land

The bog-moss plays an important part in the formation of peat. In a peat-moor the plants on the surface are the tips and branches of the very same plants whose under parts long ago died away.

When a peat-moss spore germinates in water, a meshwork of fine thread-like strands is formed, called the protonema; upon this protonema bud-like growths occur which in later stages are known as the peat-moss plants. These plants very soon lose any root-like growth which they may have possessed, and continue to grow, year after year, from the apex of the stem or from lateral branches just below the apex of the stem.

As the floating plants multiply along the borders of a body of water, extending outward over the water as an anchored raft, the immersed dead parts of the moss are continually dropping disintegrated plant-tissue and so build soil from the bottom upward. The accumulation of vegetable matter attached to the living and floating plants on the under side causes the raft to sink gradually; so gradually that the new growth always rests just at the surface of the water until the depth of the moss-raft is sufficient to permit it to reach the bottom. In time, the weight of the superimposed mass, together with chemical changes which take place in the dead plant-tissue, convert the moss plants into more or less compact peat.

Thus a border of peat-moss soil is built around the shore; and as new plants are continually growing on the water-line, forming new rafts which in turn sink and make new moss-soil, the body of water becomes gradually less until finally it disappears altogether. During this process of marsh building a "quaking bog" occurs, when the moss covers the whole surface of the water but has not yet filled up the underlying water. Both men and animals, while endeavouring to cross a "quaking bog," have sunk through the overlying moss to be entombed in the underlying peat; and, owing to the antiseptic quality of the peat, the bodies have been kept in a state of preservation for hundreds of years.

The building of bog-mosses is not confined to depressions filled with water. Strange as it may seem, it is true, that they can climb the slopes of the surrounding shore and extend the marsh up a hill. The hill-climbing character of the moss is due to its habit of absorbing water like a sponge. If one recall the moss habit of making the new growth upon the dead and water-soaked remains of the old plants, he will readily understand that it is as simple for the moss plants to grow up a slope, if it is not too steep, as it is for them to grow on a level.

The value of the bog-mosses as peat producers in the belt over which the great continental glacier swept is greater than that of any water-loving plant. It will be remembered that the great glacier of the Ice Age moved in North America from the northwest in a southeasterly direction as far down as the northern part of New Jersey, and as the climate changed and the great ice sheet receded by melting backwards to its source, it left in its wake numerous small lakes, ranging from a few feet to several miles in diameter. It is in these lakes, when not over a mile in width, that the peat-mosses have found most favourable quarters for their work, for the smaller sheets of water are less liable to be lashed into waves by the wind.

Examples of this method of marsh building are found all over the world. Professor H. W. Brewer reports finding peat-mosses building marshes on Lassen's Peak, California, at an altitude of 5,000 feet. He found Sphagnum fimbriatum on the Sierra Nevada Chain, California, at an altitude of 11,000 feet; and Sphagnum mendocinum forming swamps near King River, California, at an altitude of from 800 to 900 feet. Examples may be found on the Palisades of the Hudson and on the summits of Mount Marcy and the Shawangunk Mountains in New York, or on the Pocono Mountains, Pennsylvania.

In the pass between Mount Marcy and the highest point in New York State, and Mount Skylight, near the camp and about half a mile from the summits of the mountains, lies "Lake Tear of the Clouds." To-day it is a mere bog-hole, neither large nor deep, but when named by Verplanck Colvin not very many years ago, its clear waters nestling in a rocky basin suggested to him the pretty name. At that time a fringe of peat-moss wreathed its shores and was reflected from it as from a mirror. To-day it is surrounded by boggy shores and is dotted with little islands of similar character; its bottom is soft mud made of decayed vegetable matter. There is no visible inlet that could bring in sediment; it is fed only by the slight drainage of rain and melting ice under the rocks on the adjacent mountain sides, and yet it is never dry.