274 NEBRASKA STATE HORTICULTURAL SOCIETY. 



into the regions now characterized by the billowy hills covered with 

 the bunch-grasses and their associates. 



The Sand Hill landscape in these early days was probably a rest- 

 less maze of wandering sand dunes. In later years certain plants crept 

 in from the surrounding plains, only to be uprooted and blown away. 

 After many such invasions some individuals finally succeeded in main- 

 taining a foothold in the more protected portions of the hills. Notwith- 

 standing the terrible conditions imposed by an arid climate and a 

 continually shifting soil, vegetation continued to spread to other areas 

 from these primary centers of establishment. 



Some time after the Sand Hill flora had gained a lasting hold upon 

 the dunes and the greenish hue of vegetation had spread over the great 

 expanse of hills, enormous herds of bison came charging into the region 

 in quest of forage. The vegetation was closely grazed and tramped 

 into the unstable soil. And then the red man came, who killed the 

 bison for food, clothing and for many other useful purposes. He sought 

 to improve the range for the wild beast and for his own stock by burn- 

 ing the grass at certain seasons of the year. In this way a third and 

 still greater menace was forced upon the plants that were struggling so 

 hard to cover the Sand Hills with a permanent mantle of vegetation. 



The Sand*'Hill region of Nebraska is one of the largest and best 

 known portions of the sand hills of the Great Plains. In our state the 

 m'ain body of Sand Hills is oblong in shape with irregular margins. 

 This region lies north and west of the central portion of the state. 

 On the northern edge of the region there are numerous deep canyons 

 with steep, more or less wooded sides. A few more or less isolated 

 areas of Sand Hills occur outside this great main region both north and 

 south of the Platte, 



The Sand Hills of Nebraska cover an area of more than 18,000 square 

 miles, almost one-fourth of the total area of the state. This is about 

 equal to the combined areas of New Hampshire and Vermont. The 

 hills are all round-topped or conical and smooth, clearly showing that 

 they had been shaped by the wind long before their invasion by plants. 

 There are many depressions between the hills, many of which assume 

 the proportions of valleys more than a mile in width and sometimes 

 many miles in length. From these well-developed valleys the low places 

 decrease in both width and length until they are mere narrow, saucer- 

 shaped basins or "pockets" a few hundred yards across. The well-pro- 

 nounced valleys are, as a rule, about parallel and trend in a general 

 southeast and northwest direction. Such valleys are frequently com- 

 pletely inclosed by ranges of hills and in this way effectively sepa- 

 rated from adjacent valleys, though such may not be more than a half 

 mile distant. Sometimes instead of the valleys being separated by a 

 range of round-topped hills this is accomplished by a continuous rounded 

 ridge. The sides of these hills are often very steep, making difficult the 

 direct passage over from one valley to another. 



