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of blowouts. The successions between the basin and the blowsand 

 associations, and between the blowsand and the deposit associations, 

 may take place in either direction. The confluence of a number of 

 blowouts may cause the development of a large blowsand complex. 

 This may also result from accidental causes. Stabilization by the 

 bunch-grass may occur in any association of the blowout formation. 

 The forest formation succeeds the sand prairie either through 

 the black-jack oak or the black oak association. The association in- 

 vaded is usually the bunch-grass, though the large areas of nearly 

 bare sand may perhaps also be directly succeeded by forest growth. 

 In this type of succession a sand-thicket stage consisting of Rhus, 

 Ptclca, Robijiia, Popnlus, and other species, would probably inter- 

 vene. The successional relationships are shown graphically in Glea- 

 son's bulletin article ('10:133) by means of a diagram. 



