come more abrupt, and are more or less forested. The bluffs and 

 slopes along the river between Pratt lake and the ''big loop" 

 are also marked by frequent and sometimes extensive hillside 

 bogs. The ' ' big loop * ' of the Little Sioux sweeps around a great 

 drift ridge, the more abrupt slopes of which are heavily forested. 

 Below the ''big loop" the western bluffs, where abrupt, are spar- 

 ingly forested, as sho^vn in Plate V, fig. 2. 



Sylvan lake, Pratt lake, and Pillsbury lake are shallow, and 

 similar to the smaller lakes and kettleholes already described. The 

 groves along their shores also mark the rougher or more abrupt 

 slopes or banks, as in the cases previously noted. 



The rather narrow valley of the branch which drains the G-ar 

 lakes is practically treeless, and is bordered by rather gently 

 rolling prairie. 



Outlying points. — Two regions which lie beyond the limits of 

 the territory mapped are worthy of note because of their interest 

 to students of the Laboratorj^ as excursions may be easily made 

 to both. A brief note concerning each is sufficient. 



Ocheyedan Mound. — This is a gravelly knob southeast of 

 Oeheyedan in Osceola County. Its flora is essentially that of the 

 dry prairie hills west and north of the Laboratory. Rush lake, 

 a large shallow kettlehole, with marshy shores, lies northeast of 

 Ocheyedan. Its flora is essentially the same as that of the shal- 

 low lakes and kettleholes within our territory. 



Estherville. — The valley of the Des Moines river at Esther- 

 ville in Emmet County is of much interest to both botanists and 

 zoologists. The steeper slopes bordering the valley are heavily 

 wooded, and the alluvial bottom land furnishes both sand and 

 marsh plants. The upland prairie between Estherville and Su- 

 perior forms a part of the watershed between the Des Moines (or 

 Mississippi) and the Little Sioux (or Missouri) drainage systems, 

 and a sample of its flora is still preserved along the railway right 

 of way between these two points. 



ECOLOGICAL REGIONS 



It win be observed that the region under discussion contains, 

 within comparatively narrow limits, practically all the types of 

 ecological areas which occur in Iowa, with the exception of rock 

 ledges. Moreover the depth of West Okoboji lake, the extent of 



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