THE PBAIKIES ]_89 



and Kennebec townships in Monona county, where there are ab- 

 rupt bends in the line of bluffs, or where the latter turns to follow 

 a tributary valley, groves are well developed on the south side of 

 the crescent or valley, where the bluffs face the northwest or 

 north. A similar effect is produced by a more gentle swerving 

 of the line from the prevailing northwesterly direction, as in 

 St. Clary's township in ^Fills county, in Raglan township, Harri- 

 son county, and at various other points along the ^Missouri bluff's. 



Local illustrations of the effect of topography upon the flora 

 are abundant along the bluff's in Missouri, and several are shown 

 in the figures. Thus plate III. figure 2 sho^v^ a loess ridge at Ham- 

 burg. Iowa. Its western portion ahe left side as shown in the 

 figure; forms the bluff's of the ^Missouri valley, and is covered with 

 a typical prairie flora. The eastern slopes, sheltered from the 

 southwesterly summer winds and to some extent from the after- 

 noon sun. are more or less densely covered with a forest growth. 

 This is typical of innumerable ridges in the western part of the 

 state. 



Plate IV, figure 2 represents the bluff's north of Missouri Val- 

 ley, Iowa, looking west of north. The more remote bluff shelters 

 the forested vaUey to the right, while the bluff itself is covered 

 with a prairie flora. 



Plate V. figure 1 represents a series of loess ridges jutting into 

 a short tributary vaUey south of ^lurray hill near Little 

 Sioux. Iowa. The view was taken looking almost east. This val- 

 ley is almost continually wind-swept in the summer, and every 

 ridge which projects into it is a treeless prairie, while every shel- 

 tered ravine has developed a grove. 



Plate IX, figure 1. shows a sheltered valley just north of Mis- 

 souri Valley. Iowa, looking east. The bare ridges at 1 and 3 

 form the bluffs of the Missouri valley and are covered with a 

 typical prairie flora which is listed in the third column of the 

 table. The sheltered vaUey shows a small grove, and the edge of 

 another grove may be seen just beyond the top of ridge 1. 



Other illustrations on a much larger scale are also shoAvn in 

 other figures. Thus plate IV illustrates the opposite bluff's of the 

 Missouri valley above Omaha, looking north. Figure 1 shows the 

 sheltered bluffs extending north from Florence. Nebraska. 



