278 NEBRASKA STATE HORTICULTURAL SOCIETY. 



straight, wiry sitems in close proximity, so that a clump or bundle of 

 lifty to a hundred or more stems are densely crowded together. These 

 bunches occur more or less scattered in a way such that the character- 

 istic tufted nature of the vegetation results, and the numerous smaller 

 species that occur in the intervals are quite effectively concealed. 



A plant association composed of bunch-grasses is the typical vegeta- 

 tion of the whole Sand Hill region. This covers the hills and ridges 

 over thousands of square miles, being absent mainly from the "blow- 

 outs" and the moister A^alleys. Once established in the sandy soil the 

 bunch^rasses cope very successfully with tire fury of the wind and the 

 shifting sand. However, if fire or over-grazing seriously reduces the 

 bunches in size and vitality, subsequent winds may uproot and carry 

 them away. But on the whole the bunch-grasses are very effective sand 

 binders, and it would be a great calamity indeed if they were to be re- 

 moved and nothing substituted. It, is due to them more than to any 

 other single type of plants that the vegetation of the hills is enabled to 

 persist. Within the shelter of the bunch-grass asso'ciation valuable 

 species thrive that in its absence would never have found access to the 

 region. 



The bunch-grass par excellence is the little blue stem (Andropogon 

 scoparius), but associated with it are others, such as sand grass (Cala- 

 movilfa longifolia), and needle grass (Stipa comata). Andropogon sco- 

 parius is the dominant species throughout the region, the other species 

 being present only occasionally. It is the little blue stem that gives the' 

 first greenish hue to the sand hill landscape in the spring, and it is the 

 same species that clothes the hills with the rich reddish-purple in the 

 autumn and through the winter. Hall's blue stem (Andropogon hallii), 

 common on the upper slopes of the hills and the tops of ridges, is usually 

 of secondary importance. Its few tall whitish or bl^iish stems in poorly 

 defined bunches are, however, conspicuous wherever they are found. 



Within the bunch-grass association there are a number of secondary 

 types that are quite well defined. But as one views the vegetation of 

 the Sand Hills in a general way these are lost in the great monotony of 

 the bunch-grass association. However, the vegetation and general life 

 conditions of the uplands, the home of the bunch-grasses, are very notice- 

 ably different from those characters on the river flats or in the wet val- 

 leys. The exposure to both the drying and the mechanical effects of the 

 wind is most keenly felt on the uplands, composed of the hill tops and 

 upper slopes. Sometimes the wind sweeps over the crests of the hills 

 with such terrific force that one can not stand in its path and endure the 

 sting of the sand blast. During a bright day with a high temperature 

 and such a wind, life on the hills is well nigh impossible. During the 

 hottest days of summer the surface sand in such situations is frequently 

 heated to a temperature of 140° F. Such condition with a low water 

 content of the soil and a high saturation deficit are the factors that 

 plants must meet. One can not but admire the vegetation that possesses 

 the power of successfully resisting such a combination of conditions. 



