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THE AMERICAN BOTANIST 



valleys filled with dense thickets through which ripple clear, 

 cold brooks. Though the sand is fertile, fields are likely to 

 drift badly. Pastures are in ill repute, because of their tendency 

 to blow; and while small meadows occur, the roads are so 

 heavy that it does not pay to haul hay far. Perhaps it is the 

 impression oi irredeemable wildness that gives the sandhills 

 part of their attractiveness. 



The many differences between the adjacent grassy plains 

 and the sandhills seem to be entirely due tO' the sand. In eleva- 

 tion there is no notable difference ; it is not likely that there is 

 any more precipitation ; it is readily apparent that the sandhills 

 in general are no cooler. If this area receives no more rainfall, 

 and is not cooler whence come the increased vegetation, the 

 bountiful springs and the fresh ponds? 



The sand, being loose and porous, absorbs at once all rain- 

 fall. Even during a heavy shower no water runs off on the 

 surface. For a short time after rain the evaporation is very 

 rapid, more rapid than water can be supplied from below by 

 capillary action. Consequently the capillary tubes become 

 broken and evaporation stops long before any considerable 

 amount of the recent precipitation has disappeared. The bal- 

 ance escapes slowly from the leaves of the vegetation and from 

 the many voluminous springs which supply the brooks that 

 drain the region. 



As might be expected the air temperatures become very 

 high especially in the blowouts during sunny days. This super- 

 heated air rises to join the general wind and as a result the 

 winds blowing across the sandhills are exceedingly drying and 

 the vegetation must either because of an abundant supply of 

 available moisture, be able to endure rapid evaporation or it 

 must be able to resist drying by possessing restrictions against 

 evaporation. Both types are found. The bunch grass, roses, 

 bush morning glory, sunflower, and thistle are examples of the 

 former; the cacti, sand cherry, yucca and prairie pink are 



