220 ILLINOIS STATE ACADEMY OF SCIENCE 



and beyond that a swamp zone with swamp fern and 

 sedges and some iris and swamp cinquefoil along a small 

 drainage ditch. The edges of the bog are now being 

 drained toward the center, but the draining of the whole 

 bog would be an expensive matter owing to the height of 

 the surrounding ridges. The surface has been burned 

 repeatedly and the swamp zone is now occupied by a 

 scanty growth of ruderals. 



About one half a mile to the west of these two bogs is 

 a long L-shaped depression which contains two separate 

 tamarack groves indicated on the map (Fig. 6) and 

 originally referred to as No. 7 and 8. One is long and 

 L shaped, running north and south, and the other, ap- 

 proximately round, at the end of the western arm of the 

 depression. The north end of the depression is large and 

 rounded and the tamarack grove occupies only the west- 

 ern half of this enlargement, while the eastern half con- 

 tains a crescent shaped pond which narrows rapidly 

 toward the south and disappears about the middle of the 

 tamarack forest. 



The substratum is fairly solid under the tamaracks, and 

 its upper surface consists largely of tamarack needles 

 but below it is composed of dark brown peat. Both at the 

 surface and below to a depth of six feet it gives a neutral 

 or alkaline reaction. On the east side of the tamaracks 

 between the forest and the small lake is a small morainic 

 knoll covered with oaks, and beyond this knoll the sub- 

 stratum becomes a quaking mat which contains no char- 

 acteristic bog plants and is underlain by a soft muck 

 which is strongly alkaline and contains many small, 

 white, calcareous fragments apparently of gastropod 

 shells. This swamp mat surrounds the southern pointed 

 end of the lake and in that locality contains dense colon- 

 ies of cattail, bulrush and reed grass (Phragmites). The 

 main body of the mat consists of grasses and sedge and 

 swamp mosses with some swamp cinquefoil, St. John's 

 wort and several colonies of fringed gentian. 



The tamarack forest has been cut in places, but where 

 relatively untouched the growth is dense and contains 

 many trees up to 10 and 12 inches in diameter, with at 

 least one of twenty inches. A 4-inch stump showed 40 or 



