[Vol. 10 



386 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



Between the Turtle Mountains and the Missouri Plateau lies 

 the broad flat plain of the Mouse River occupying the basin of 

 the glacial Lake Souris which extended northward into Canada. 



The lakes considered in the present report are found in the 

 drift prairie plain and Turtle Mountains. The drainage of the 

 areas is very poor and numerous depressions among the hills 

 form the basins of many of the lakes. While most of them are 

 merely depressions in the land filled with water, there are several 

 which are either expansions of an existent river near its head- 

 waters, or which occupy portions of an old river channel. The 

 largest of these are Devils Lake and Stump Lake, which were at 

 one time parts of the much larger glacial Lake Minnewaukon, 

 draining into the Sheyenne River. 



Another group of these lakes is found in the course of the James 

 River, north of Jamestown, and comprises Arrowhead, Jim, and 



one or two smaller lakes. 



Spirit wood I and II and a number of neighboring lakes probably 

 occupy an old river valley and the same is very evident in the 

 case of Strawberry, Long, Crooked, and Turtle Lakes, north of 

 Washburn. 



Most of the lakes are shallow, having a depth of not more 

 than 3-4.5 meters, while many are merely shallow pools which 

 dry up in dry years, but may have a considerable extent in 

 years of heavy rainfall. The deepest of any is Alkali Lake, II, 

 which has a maximum depth of 27 meters. Their supply comes 

 partly from springs, partly from run-off of rain or melting snow. 

 In most cases this supply is inadequate to meet the demand and 

 the lakes are gradually drying up. This is notably true of such 

 highly alkaline bodies as Devils and Stump Lakes, but even in 

 the case of spring-fed, freshwater lakes in the Turtle Mountains 

 there has been a marked decrease in level in recent years. This 

 drop may be due in part to the general lowering of the water 

 table throughout the state in recent years, which in turn is 

 probably due to continued opening of new artesian wells and 

 their uncontrolled flow. 



Most of the lakes under consideration have no outlet and this, 

 coupled with their decrease in level in many instances, has led 

 to the high concentration of salts present in so many of them. 



