1. Bacon's Swamp is now occupied by a group of associations characteristic of half-drained swamp areas of the central west. 2. The vegetation in the past has pertained more to the character of undrained swamps. Evidence of this rests on the following points: (a) the luxuriant growth of Sphagnum some 20 odd years ago, and its known presence up to 7 years ago; (b) the presence of quantities of well preserved Sphagnum remnants in the surface and deeper layers of the peat, particularly in the deeper southwest lobe of the swamp; (c) the higher acidity of the surface water, which is a result of the even higher acidity of the underlying peat; (d) the topography of the peat, which is more characteristic of the type of filling-in found in bogs than in ordinary lake deposition, in that the higher portion of the peat is in the center of the swamp and diminishes toward the periphery, until there is a moat filled with 4 or 5 feet of water which entirely surrounds the wet meadow. 3. There has been a recent lowering of the water table (sometime within the last quarter of a century) which may be taken to account for: (a) the disappearance of the Sphagnum; (b) the restriction of the buttonbush to the moat, that is, the elimination of it from the wet meadow, accompanied by the spread of the Calamagrostis group. 4. The climatic conditions in the vicinity are such as not to preclude the presence of bog vegetation. 5. The hydrophytic succession, found particularly in the middle and northern, less acid, parts of the swamp, progresses from (a) submerged aquatics; (b) rooted aquatics with floating leaves; (c) floating aquatics; (d) rooted aquatics, first with broad erect leaves and later with taller narrow leaves; to (e) the meadow with Carex around the deeper margin, and Calamagrostis, etc., in the center. These steps are related consecutively to decreasing water depth, with shading as a factor. 6. From Typha there seems to be another sequence not definitely related to the one just described, but which starts with the moat and works outward. It consists of (a) Typha, (b) Cephalanthus, (c) Salix, (d) swamp forest, and (e) upland climax forest. The early stages of this sequence seem to have been eliminated by the encroachment of the vegetation of the peat mat in the center. The region of these outer zones has probably never shared in any of the bog history of the central part of the swamp.