576 



under whose joint supervision the main part of the investigation was 

 pursued, and also to Dr. J. M. Greenman, of the Missouri Botanical 

 Garden, for certain assistance in taxonomy. 



General Features oe Skokie Marsh 



Skokie Marsh* is intimately associated with Skokie Stream — a 

 small sluggish meandering stream beginning west of Waukegan, 111., 

 and extending southeast. Years ago this stream doubtless flowed 

 on until it at last joined the East Branch of the North Branch of 

 the Chicago River. Today, however, its identity as a stream is lost 

 at a point west of Glencoe, 111., where much of the water spreads 

 itself over the marsh or enters some of the artificial drainage ditches. 

 Figure 17, Plate XCIV, shows a more or less artificial basin at the 

 south end of the marsh (west of Winnetka), in which water col- 

 lects, flowing thence southward through a ditch. Southwest of 

 Winnetka (west of Kenilworth and Wilmette), several broad drain- 

 age ditches may be seen. These receive much of their water, in cir- 

 cuitous ways, from Skokie Marsh and pass it on, all of it coming 

 sooner or later into the North Branch of the Chicago River. One 

 of these drainage ditches is shown in Figure 14, Plate XCII. 



In recent years drainage and cultivation have been carried on to 

 such an extent along the margins of the marsh that its areal limits 

 can be defined only arbitrarily. As shown in the accompanying map 

 (PI. LXXXVI, Fig. i) however, it is approximately 12 km. long, 

 and at its southern end becomes 1.5 km. wide. For the naturalist, 

 access to the marsh may be had at all times by means of the several 

 roads running east and west directly across it. The scenery along 

 certain of these roads (PI. XCIII, Fig. 15) is particularly pleasing. 

 During spring and autumn, the ditches running along either side 

 of the roads are usually filled with water. In some of these the 

 water is deep enough to permit the passage of a small boat. In 

 the spring of 191 2, when the marsh was in many places under water, 

 a boat (PI. XCIII, Fig. 16) was found very convenient for pene- 

 trating to the interior. 



In early postglacial times, the marsh was an embayment (Atwood 

 and Goldthwait, '08, p. 58), which later disappeared and gave place 

 to a system of drainage. At present the surface soil almost through- 

 out the marsh consists of a black muck or partially decayed peat, 

 I m. or less in thickness. Underneath is a subsoil of glacial clay. 



*For many additional data and photographs of Skokie Marsh, see Baker ('10), 

 who has given also an account of its zoological aspects, with special reference to 

 the moUuscan fauna. 



