374 Prairie Legumes 



Red River valley, the ancient bed of the glacial Lake Agassiz. The 

 observations noted in this paper are more pertinent to the high rolling 

 prairie regions lying south of the Red River valley proper. These 

 prairies are practically all of a drift formation. The regions to the 

 north of them, or perhaps western Minnesota itself, seems at one time 

 to have been underlain by extensive formations of limestone which 

 became food for the glacier, and was ground up and incorporated with 

 the other materials in such a way as to produce a soil of surpassing 

 fertility. In respect to the amount of decomposing limestone found 

 in the soil, western Minnesota differs markedly from eastern Minne- 

 sota, or from Wisconsin, and the difference is all in its favor. An 

 outcrop of granitic rocks crosses the state from its northeast corner 

 to its southwest corner, but the material from which the extra- 

 ordinarily fertile soil of western Minnesota was formed was very 

 largely sedimentary rocks abounding in carbonate of lime. Very 

 few exposures of this rock are now to be found remaining in place. 

 There is found on the northeasterly side of Big Stone lake about 

 half a mile from its head an outcrop of shale bearing many concre- 

 tions, apparently gypsum crystals, but the exact nature of these so 

 far as the writer knows has not been determined. Prof. Todd of 

 the United States Geological Curvey is of the opinion that this outcrop 

 is Carlisle shale of the Benton group. Should this opinion prove 

 to be correct one might hazard a guess that the immense number of 

 large and powerful springs found along the southwesterly side of 

 Big Stone lake are due to the running out in this locality of the 

 water bearing Dakota sandstone. 



Rich as this soil is minerally, it is probable that part of its fer- 

 tility is due to the action of nitrifying bacteria which found con- 

 genial hosts on the roots of leguminous plants formerly so abundant 

 on the prairie, Thic is merely suggested without any purpose of 

 going into the extensive literature of this branch of the subject. Cer- 

 tain it is that those parts of the prairies lying highest and driest 

 and apparently possessing the least fertile soil have produced the best 

 crops for many years, some having stood continuous wheat cropping 

 for forty years. Lands lying on a somewhat lower level and appar- 

 ently possessing much more soil humus, have not been nearly so 

 productive; and it is a fact that the original prairie sod in such 

 locations did not contain nearly so many leguminous plants. It has 

 been noticed, too, that those portions of the original prairie that have 

 been fenced and long pastured and afterwards broken up and planted 

 to ordinary farm crops have not been nearly so productive as the 

 prairies that were broken without being pastured. It is reasonable, 

 to believe that there must be some connection between this lack of 

 fertility and the fact that the leguminous plants were so quickly 

 destroyed by cattle. 



Like the buffalo the leguminous flora of western Minnesota has 

 now practically passed away, and the traveler on the prairies sees 

 only farm crops, or waste pieces of land bearing weeds of various 

 kinds, many of them bing immigrants from Europe. It seems proper 

 to put on record some account of these plants before the memory of 

 them entirely dies out. They practically exist now only in herbaria, 



