573 
develop, but this fact has no bearing upon the explanations of causes 
of the original prairies and forests of the state. 
The progress of civilization during the last century has not only 
destroyed nearly all of the native prairies of the state but, likewise, some 
of the conditions that gave rise to them. Grazing, drainage, cultiya- 
tion, and stream pollution have all been destructive to the native prairie 
flora. Cultivation has destroyed the prairie plants except along fences 
between the farms, while grazing has destroyed even these last remnants 
not reached by the plow. Intensive grazing accompanied by the introduc- 
tion of blue grass and red top destroyed practically all of the native prairie 
plants on the farms not cultivated. The bluestem prairies became blue- 
grass pastures, and where drainage accompanied grazing the native 
plants of the sloughs weré also replaced by blue grass. In areas too wet 
for blue grass, red top became abundant, while in still wetter areas sedges 
and rushes prevailed. The bulrushes were mostly killed by the tramping 
of cattle, and cattails became abundant in the undrained sloughs. Graz- 
ing on the sand prairies destroyed the bluestem, and blue grass became 
abundant, giving rise to blue-grass pastures on sand. But where the 
sand areas were still too dry for the bluestems, grazing has increased 
the number of blowouts in the sparser vegetation of plains grasses. Some 
of the bluestem prairies on sand were cultivated instead of pastured. 
This has led (1) to the destruction of much of the humus accumulated 
for centuries by the decay of the native grasses, and (2) to the ex- 
posure of loose sand to wind action through the destruction of the 
prairie turf. As a result, blowouts and sand dunes become increasingly 
abundant, and the farms must shortly be abandoned. Carefully con- 
ducted experiments would undoubtedly result in the discovery of more 
profitable methods of dealing with these sand areas. 
The changes brought about by drainage are somewhat too com- 
plicated to be discussed in detail in this summary. Artificial drainage 
has lowered the water-table several feet and drained most of the sloughs. 
This has led to all degrees of destruction of the natural grasses of the 
sloughs and made conditions favorable for the migration into them of 
plants characteristic of better-drained soils. Artificial drainage led to 
a sudden disturbance of the balance that obtained under natural con- 
ditions, and plants that reproduce most readily had a chance to become 
prominent. As a result, many plants not prominent on the natural prai- 
ries became temporarily abundant on the newly drained areas. This 
condition is well represented on the railway rights-of-way today. Arti- 
ficial drainage is also favorable to the development of forests on the wet 
prairies. 
The effect of the pollution of streams and prairie ponds received 
little attention in this survey. It appears to have been destructive to 
bulrushes and favorable to the growth of cattails. Its chief economic 
eifect is to be found in the destruction of algae, the main source of the 
food of fishes. 
