222 ILLINOIS STATE ACADEMY OF SCIENCE 



and many colonies of pitcher plants. A peculiar feature 

 of this bog is the tendency of several species to form 

 dense local colonies of almost pure stand. Among such 

 species were noted dwarf birch, andromeda, dewberry, 

 marsh fern, and violet ; and cattail in the swamp zone on 

 the northwest. Less common species were cotton grass, 

 swamp cinquefoil, and the mosses Polytrichum and 

 Leucobryum, a few saplings of trembling aspen, two 

 willows, and one specimen each of winterberry and moun- 

 tain ash. 



A very dense belt of shrubs, almost as long as the bog 

 mat and ranging from 15 to 30 feet wide, runs parallel 

 with the southeast side of the oval and about 20 feet 

 within it. 50 to 75% of the specimens are dwarf birch 

 which grows there very dense and 5-7 feet high. There 

 were also much winterberry, chokeberry, some elder, five 

 or six oaks 10 feet high, and many trembling aspen sap- 

 lings. The ground occupied by this shrub belt seemed to 

 be a low sand bar rising a foot or two above the level of 

 the mat, but as no borings were taken at this bog, the un- 

 derground topography can only be guessed at. 



DISCUSSION AND CONCLUSIONS 



The chief interest in these bogs lies in the fact that 

 they are the only examples remaining in Illinois of a type 

 of plant formation common in most of our northeastern 

 states and very abundant farther north. The distribu- 

 tion of deep peat deposits as shown by the soil map of 

 Illinois would indicate that these bogs were much more 

 common in Illinois in fairly recent geological times, 

 though a careful examination of the peat would be neces- 

 sary to determine whether it was formed in a bog or in a 

 swamp. 



The correlation between chemical condition and depth 

 of the substratum and the character of the vegetation is 

 important on account of its bearing on the theories of the 

 causes of xerophytism in bog plants. In these bogs the 

 substratum on which the bog plants grow is found to be 

 of considerable depth and acid in character, while the 

 swamp plants are found on a shallow substratum which 

 gives a neutral or alkaline reaction. 



