354 MINNESOTA BOTANICAL STUDIES. 



nesota slough, is about twelve miles in length. There are 

 three small branches, one of which has, within the last decade, 

 become considerably smaller than it formerly was, on account 

 of the drying up of several springs near its source. The 

 amount of water discharged from each of the two main creeks 

 during the summer months is probably not less than 1,500,000 

 cubic feet per day. Neither creek is very susceptible to 

 changes of season, but either one will rise very rapidly after a 

 sudden heavy rain-fall and return to its usual level in a few 

 hours. 



The bluffs are high and steep, and not adapted to cultivation. 

 (Plates XXII. and XXVI.) However, many of the ridges are 

 cultivated and form some of the best farms in this part of the state. 

 The valleys being subject to overflow and the bluffs very steep, 

 by no means the entire area is adapted to cultivation. This 

 condition is very favorable for the collection of native plants. 



The valleys are narrow, in no place exceeding a mile in 

 width from the brow of one bluff to the brow of the one op- 

 posite. 



In taking a view of the ecological groups of the plants in- 

 habiting this region, the territory may, for convenience, be 

 divided into river valley, creek valleys and bluffs. 



The river valley is so distinct from the creek valleys that it is 

 almost imperative that it be considered separately. The bluffs 

 along the river vary somewhat from the other bluffs, but not 

 sufficiently to warrant a division into river bluff and creek 

 bluff. 



River valley. In the river valley I include the area from the 

 foot of the bluffs on one side of the river, to the foot of the 

 bluffs on the opposite side, not including any tributaries. Along 

 this stretch of the river, from New Albin, Iowa, to Brownsville, 

 Minnesota, the valley varies from three to five miles in width. 

 The main channel of the river is from one-half a mile to a mile 

 wide. The remainder of the area between the bluffs is formed 

 of islands, sloughs and lakes during most of the year. (Plate 

 XXV., B.) During the spring and early summer the whole area 

 is generally flooded so that collection can be carried on only dur- 

 ing the late summer and autumn. The river channel proper is 

 not a fruitful field for the collection of higher plants. The 

 sluggish sloughs, lakes and ponds, however, offer excellent 

 conditions for such collection. 



