THE DECIDUOUS FOREST CLIMAX. 193 



These comprised a drained swamp in northern Michigan characterized by 

 Larix, Thuja, and Picea, Cassandra, Potentilla, Cornus, Alnus, and Salix in the 

 shrub zone, Phragmites, Typha, Sdrpus, and Menyanthes, with Sagittaria and 

 Iris in the reed zone, and Nymphaea, Nuphar, Potamogeton, Vallisneria in the 

 open water. The imdrained swamp on an island of Lake Michigan was also 

 occupied by Larix and Picea. The pioneer Sphagnum is quickly followed by 

 Vaccinium, and this forms a foothold for Cassandra and other heaths. Larix 

 and Picea occur beyond this zone, and are themselves surrounded by the climax 

 forest of maple-beech-hemlock. In an old "ox-bow" lake of the Mississippi, 

 the pioneer floating and amphibious plants are Nelumbo lutea, Sdrpus mari- 

 timus, Jussfiaea repens, and Heleocharis. The second zone is dominated by 

 Carex, with which occur Polygonum, Boehmeria, Apocynum, Hibiscus, Amorpha, 

 and Bidens. The shrub zone is marked by Amsonia, Cephalanthus, and Salix 

 longifolia. Behind this is the forest zone of Platanus ocddentalis, Acer rvbrun}, 

 and Populus deUoides. A swamp in extreme southeastern Missouri showed 

 Myriophyllum, Ceratophyllum, Potamogeton, and Cabomha in the open water. 

 These were quickly followed by Polygonum densiflorum and Zizaniopsis 

 miliacea as the water became more shaUow and quiet. Typha and PeUandra 

 may be associated with the Polygonum, as may Saururus also. Salix first 

 forms the shrub zone, followed closely by Cephalanthus, and these are succeeded 

 by the trees of the swamp land, viz, Nyssa uniflora and Taxodium distichum. 



Schaffner, Jennings and Tyler (1904 : 154) have described the succession 

 represented by the concentric zones of Brush Lake in Ohio. The zones and 

 their dominants are as follows: 



1. Submerged zone: Potamogeton, Ceratophyllum, Myriophyllum, Chara. 



2. Water-lily zone: Nymphaea, Castalia. 



3. Half-submerged zone: Bum^x, Polygonum, Typha. 



4. Decodon zone: Decodon, Solarium dulcamara. 



5. Uliginous zone : Carex, Heleocharis, Sdrpus, Eguisetum fluviatile. 



6. Shiub zone: Salix, Cephalardhus, Camus, Rosa. 



7. Forest zone: Acer, Ulmus, Fraxinus, Salix. 



Weld (1904) has distinguished the following successional zones about a 

 Michigan lake : 



(1) Potamogeton zone; (2) Nuphar zone, in which Nuphar is locally replaced 

 by Nymphaea or Brasenia; (3) Car ex-Sphagnum zone; (4) Cassandra-Sphagnum 

 zone; (5) tamarack forest. In the latter are appearing Prunus serotina, Acer 

 dasycarpum, Populus tremuloides, and Quercus rubra, indicating the course of 

 further development. 



Brown (1905) has described the development of the vegetation in peat-bogs 

 and on flood-plains in the valley of the Huron River: 



The first stage consists of Potamogeton, which is followed by Castalia and 

 Nymphaea, with which are associated tftricularia, Lemna, Spirodela, and 

 Riccia. In some places the third stage is formed by species of Polygonum 

 which tend to form a firm mat on the water. The fourth stage is represented 

 by Typha and Sparganium, together with Carex, Potentilla, etc. This is 

 followed by swamp thicket composed chiefly of Salix with a large number of 

 associated herbs. The final stage of the swamp is characterized by Larix 

 laridna, the tamarack. On the flood-plain, the sedge-swamp is replaced 

 largely by turf-forming grasses. These are followed by the elm-ash-maple 

 association in certain areas, and by the wahiut association in others. 



