THE DECIDUOUS FOREST CLIMAX. 197 



has increased greatly in consequence of the cultivation of the upland. Thia 

 leads to the entrance of the stream-swamp flora after the upbuilding of the 

 marshes. Acer nibrum is the first tree to enter the marsh formation, while 

 the foremost plant in the advance of the marsh vegetation over the water is 

 Spartina strida maritima. Rapid upbuilding of the bottom gives rise to sand- 

 bars or spits which maintain a xerophilous vegetation, and develop a forest 

 covering much more directly and rapidly than do the newly formed marshes. 



Brown (1911 : 339) summarizes succession in the lakes of North Carolina as 

 follows: 



"The whole of the bottom of Lake Ellis is covered with vegetation. There 

 are three distinct zones or successions occurring in the same depth of water, 

 but on different soils. The central zone, found on the sandiest soil, is charac- 

 terized by Eriocaulon compressum, Eleocharis robMnsii, a,nd Myriophyllum. 

 The intermediate zone, on muddier soil, is characterized by Philotria minor, 

 Sphagnum, Eleocharis interstincta, Panicum hemitomon, Nymphaea advena, and 

 Castalia odorata. The marginal zone, found on the muddiest soil, is composed 

 mostly of grasses and sedges, the chief component being Sacciolepis striata. 



"The disposition of the three zones seems to be determined by the character 

 of the soU. The plants of the intermediate zone invade the territory of the 

 central as it becomes muddier by the depositing of debris, while the plants of 

 the marginal zone in turn invade the territory of the intermediate. As this 

 invasion continues the grasses and sedges will occupy more and more of the 

 lake and probably wUl finally drive out the plants of the other zones. The 

 vegetation in the lake is of recent origin and the invasion seems to be going on 

 rapidly. A few small plants of Pinus serotina, Acer riibrum, and Ldguidambar 

 styraciflva are found when the soil comes near the surface of the water. 



"Pinus serotina and Ldquidambar styroicijlua are invading the growth of 

 grasses and sedges from the outer edge. 



"The emergent vegetation growing in Great Lake consists of Taxodium dis- 

 tichum, Nymphaea advena, Panicum hemitomon, and Xyris caroliniana. The 

 aquatic vegetation is very scanty. In the shallow water this is probably due 

 to the hard, shifting sand which forms the bottom, while in the deeper parts 

 of the lake where the bottom is muddy, the dark color of the water probably 

 excludes too much sunlight to allow the growth of plants. 



"The shore of the eastern half of the lake is covered with large trees under 

 which there is a dense undergrowth. The shore of the western half is covered 

 with low bushes and briers and a few small pine trees. The scarcity of trees 

 here seems to be due to forest fires, which sweep over this part of the shore, 

 whereas the other half is protected by swamps." 



Bums (1911 : 105) has Usted the characteristic and principal species of the 

 successional zones of the bogs of southern Michigan: 



I. Zone of submerged plants: Chora, CeratophyUum, Naias, Potamogeton. 

 II. Zone of water-UUes: Castalia, Nymphaea, Bra^enia. 



III. Zone of floating sedges: Carex filiformis,C.oligosperma, with Menyanthes, Duli- 



chium, Eriophorum, Drosera, etc. 



IV. Zone of bog-shrubs: Chamaedaphne, Andromeda, Betida, Nemopanthes, Vaccin- 



ium, Sarracenia. 

 V. Zone of tamaracks: Larix, Cornus, Osmunda, Rhus, etc. 

 VI. Zone of poplars and maples: Acer, Populus, Prunus, Quercus, Sambueus, Salix, 



Spiraea, Cephalanthtis, etc. 

 VII. Zone of marginal willows: Salix, Cornus, Ilex, Buhus,Rosa, etc. 



The author concludes that these bogs are not xerophytic habitats, but that 

 they contain xerophytic, hydrophytic, and even mesophytic areas, though the 



