bog, very old lake without inlet or outlet that becomes acid and is gradually overgrown with a characteristic vegetation (see swamp). Peat moss, or sphagnum, grows around the edge of the open water of a bog (peat is obtained from old bogs) and out on the surface. With its continued growth, the moss forms a mat on the water in which other bog plants find a foothold, and humus and soil are slowly built up on the body of the water. Because of this formation bogs are sometimes treacherous (quaking bogs shake under the weight of a man) and have occasionally resulted in fatalities when a man or animal breaks through the vegetative crust. Because of their extreme acidity, bogs form a natural preservative and have been found to be a valuable repository of animals and plants of earlier times. Typical bog plants of today include, besides sphagnum, many orchids, the pitcher plant, the sundew, and the cranberry (old bogs are utilized for cranberry cultivation). Because of the reclamation of old bog lands by drainage and by their natural filling in, bogs in America are becoming rare, and with them their unique flora and fauna. One example of the latter is the bog turtle, Clemmys muhlenbergi, a tiny animal with a black, sculptured shell and orange head markings. The bog turtle has disappeared from most of its original habitat in the middle Atlantic states. Another consequence of the drainage and filling of bogs is the decreased water-holding capacity of the land, resulting in rapid run-off during rains and the increased siltation of rivers and streams.