1920] TAYLOR— SUCCESSION OF MOSSES 483 



and other factors of environment do not differ widely in the three 

 areas, only five moss species have so far been found common to 

 all. These are Ceratodon purpureas, Mnium cuspidatum y and 

 Catharine a undulata on higher land or on logs, and Brachythecium 

 rutabulum and Amblystegium radicale in low wet places. All 

 except the first are mesophytic species. The Ceratodon occurs 

 rarely and then on sticks which are in rather dry locations in the 

 open or along the margin of the swamps. Sphagnum and Leuco- 

 bryum are found only at Thornton, the former growing on the 

 ground in depressions, and the latter on hummocks. Wilhelm far 

 surpasses the other forests in the total quantity of the moss flora. 

 Thuidium delicatulum grows abundantly on decaying logs and 

 occasionally on the ground, and is perhaps the most conspicuous 

 species with the exception of Mnium cuspidatum. Thuidium 

 recognitum and Anomodon rostratus are found in smaller quantities, 

 usually on logs or tree bases.. Several of the very mesophytic 

 species, such as Climacium americanum and Rhodobryum roseum } 

 are common both on logs and on the ground. The shade is dense, 

 and decaying plant material forms a thick layer on the forest 

 floor. The moss display is of greater luxuriance than elsewhere 

 in the Chicago region and is a close rival of that of the Carroll 

 Creek ravine. 



Bog forests. — The two bogs studied within the limits of the 

 region under consideration are the tamarack bog of Mineral Springs 

 and the Sphagnum bog near Hillside. Several typical associations 

 in the ecological development can be distinguished : the sedge mat, 

 shown at Mineral Springs; the shrub stage, well developed in both 

 bogs; and the tamarack tree association at Mineral Springs. An 

 additional division might be made of the Sphagnum moss associ- 

 ation at Hillside, but this is a slightly different line of development 

 rather than another ecological association. 



As stated before, the bog successions are distinguished in 

 origin from the pond successions, in that they are formed on 

 sedge mats which grow out over the surface of deep lakes, form- 

 ing quaking bogs, which may remain in a very unstable con- 

 dition for many years. The first association to be found at Mineral 

 Springs at the present time is a mixture of bulrushes, cat-tails, and 



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