included in the accompanying map lies Trithin the border of the 

 Wisconsin drift sheet, which here presents a more or less broken 

 or nndnlating surface the depressions of which are occupied by 

 numerous lakes, ponds, and swamps. As may be observed by 

 consulting the map, it contains three large lakes, nameh^ West 

 Okoboji, East Okoboji, and Spirit lakes, and a large number of 

 smaller bodies of water ranging in size from Center lake, which 

 is a very considerable body of water, to small "kettle-holes," 

 such as are especially abundant between Center lake and West 

 Okoboji lakes, and west of the latter lake. 



Spirit lake is the largest of the lakes in superficial area, but it 

 is comparatively shallow, its greatest depth probably scarcely 

 reaching 40 feet. Its comparatively regular outline presents 

 few bays and coves, in the shelter of which many aquatic plants 

 thrive best, and this coupled with the prevailing sandy or grav- 

 elly shores and bottom, and the greater exposure of the surface 

 to storms, probably accounts for the lesser variety and abundance 

 of aquatic plants in this lake. The northeastern part of the lake 

 is probably the richest in flora, and here beds of rushes and other 

 aquatic plants are locally well-developed. 



The northern and northeastern shores of the lake are low, 

 ^vith sandy or mud beaches, and outlying pools and swamps 

 which are usually crowded with plants. The south shore of the 

 northeast bay is bowldery. The banks of the southeastern shore 

 are abrupt, and in some places rise to a height of 20 feet. The 

 southern shore is a rather flat, bowldery and sandy beach (see 

 Plate VI, fig. 2), which is continued southward as a flat sandy 

 prairie to meet the north beach of East Okoboji lake. The en- 

 tire western shore is bordered by more or le&s interrupted abrupt 

 banks which reach a height of 10 to 25 feet, and at one point 

 north of Templar Point, fully 30 feet above the lake. Occasion- 

 ally a low draw, forming a swamp or pond, appears as an outlier, 

 or connects vdth. the lake, as west of Templar Point and in other 

 localities northward. Northwestward the territory bordering 

 the lake becomes rougher, and its depressions are occupied by a 

 series of smaller lakes of great interest. These lakes are all 

 shallow, and as the summer advances, and during dry seasons, 

 broad, sandy, or more frequently muddy flats are exposed. 

 These fluctuations in level check the development of many plants 

 along the shores, but in the somewhat deeper, more permanent 



5 



