308 MINNESOTA BOTANICAL STUDIES 



meadows arising from invasion by Stipa and Agropyron have been 

 observed in a number of places. These facts lead to the tentative 

 conclusion that the final vegetative cover of the sandhills may be 

 composed of one or more of the sod-forming prairie-grass associa- 

 tions and the bunch-grasses will remain as relicts upon the more 

 extremely xerophilous, sandy situations. 



Thus it appears from the data collected during the prelimin- 

 ary investigation of the structure and development of the vegeta- 

 tion of the sandhills of Nebraska that we have here two prominent 

 successional series. One of these originates under the peculiar 

 xerophilous environment of a sand dune complex, while the other 

 begins in an extremely hydrophilous situation. And furthermore, 

 as a tentative conclusion, it appears that each of these series pro- 

 gresses toward, and will ultimately culminate in, the relatively 

 mesophytic sod-forming associations of the prairie-grass formation. 



LITERATURE CITED OR CONSULTED 



1. Alway, F. J., and Bishop, E. S. The nitrogen content of some 

 Nebraska soils. Ann. Rep. Neb. Agri. Expt. Sta. 1912. 



2. Barbour, E. H. Nebraska geological survey I. Report of the 

 state geologist. 1903. 



3. Bates, C. G. Experiments in sandhill planting. Proc. Soc. 

 American Foresters V., No. 1. 1910, 



4. Bates, J. M. The grasses of northwestern Nebraska. Ann. Rep. 

 Neb. State Board Agri, 1892. 



5. Bishop, E. S. See Alway, F. J., and Bishop, E. S. 



6. Belz, J. O. See Briggs, L. J., and Belz, J. O. 



7. Bessey, C. E. Grasses and forage plants of Nebraska Ann. 

 Rep. Neb. State Board Agri. 1886. 



8. . Eastward extension of Pinus ponderosa in Ne- 

 braska. Am. Nat. 21 : 928. 1887. 



9. . Westward extension of Juglans nigra in Ne- 

 braska. Am. Nat. 21 : 929. 1887. 



10. . The grass flora of the Nebraska plains. Am. 



Nat. 22:171. 1888. 



11. . The bearberry in central Nebraska. Am. Nat. 



25:1130. 1891. 



12. . The re-foresting of the sandhills. Ann, Rep. 



Neb. State Board Agri. 1894. 



