THE PRAIRIE FLORA OF SOUTHWESTERN MINNESOTA. 



L. R. Moyer, Montevideo. 



In its physical features western Minnesota is an undulating plain 

 lying about 1,000 feet above the ocean level. This plain is of glacial 

 origin,, and consists of blue and yellow till, probably underlaid with 

 beds of Cretaceous rock. Entering the state about thirty miles south 

 of Big Stone lake and extending southeasterly toward the southern 

 boundary of the state is a great terminal moraine known to the early 

 voyageurs as hte "Cateau des Prairies." In the western part of Lin- 

 coln county the Coteau rises to the hight of about 1,900 feet. The 

 northeasterly slope of the Coteau consists of till containing many boul- 

 ders — worn and rounded by the glacial waters. Some of these boul- 

 ders are of granitic rocks similar to the rocks in the northern part 

 of the state, and others are of magnesian limestone — such as are not 

 now found in place nearer than at Winnipeg. 



Another terminal moraine known to geologists as the "Dovre mor- 

 aine" extends from a point in Kandiyohi county north of Willmar, 

 northwesterly through Swift, Pope and Douglas counties, and culmin- 

 ates in the Leaf hills in the southern part of Otter Tail county, where 

 an elevation of 1,750 feet is reached. 



Between the Leaf hills on the north and the summit of the Co- 

 teau des Prairies on The south lies the Minnesota valley. This valley 

 in western Minnesota has a width of about 120 miles; and through 

 the center oi this region the Minnesota river — or more properly the 

 glacial river which preceded it — has eroded a deep channel, cutting 

 through the drift, and through the geologically recent rocks on which 

 the drift is super-imposed, down to the original Archean rocks which 

 appear to cross the state from the northeast to the southwest. These 

 rocks are exposed in great ledges at Beaver Falls, Granite Falls, Mon- 

 tevidio, and Ortonville. This river bed or channel is from 100 to 

 200 feet in depth and will average about one mile in width. In many 

 places the bluffs are quite abrupt, and in other places they have be- 

 come much worn down. A great river once occupied this valley ex- 

 tending across from bluff to bluff, and was the outlet of a great lake 

 which covered all the Red River country. This great lake is known 

 to geologists as Lake Agassiz and the ancient river has received the 

 name of the River Warren. The Minnesota river which now occupies 

 this great channel is a typical prairie river. In midsummer when it 

 is dry, and likewise in winter when its affluents are frozen up it is an 

 insignificant stream; but when a heavy snowfall melts in April with 

 unusually heavy spring rains it is still capable of becoming a great 

 stream sweeping everything before it. 



