200 



MINNESOTA BOTANICAL STUDIES 



from about 1,800 feet along the eastern border to al)out 4,000 feet 

 across the western portion. The places of i^reatest relief in the re- 

 gion are in the gorges of the Dismal and Snake rivers where the 

 surface of the stream which has cut far into the Loup Fork Beds 

 lies from 300 feet to 380 feet or possibly more below the crests of 

 the highest near-by hills. The Snake River canyon is in some por- 

 tions characterized by almost perpendicular clififs capped by enor- 

 mous hills. 



Fig. 3. Topographic features. A township within the hay meadow region. 

 Note the broad valleys and ranges of hills. Contour interval 20 

 feet. (Somewhat idealized.) 



The sandhills are characterized by sub-surface drainage. The 

 loose porous dune sand of the uplands soaks up precipitated moist- 

 ure very rapidly so that after the heaviest falls of rain scarcely any 

 water is drained from the surface but all of it sinks quickly into 

 the open soil. The soil is quick to lose its water by percolation to 

 deeper levels, thus leaving a minimum quantity permanently in the 

 capillary zone. But a short time is therefore required after even a 

 heavy rain for the penetration of the moisture to a depth below the 



