202 



BOTANICAL GAZETTE 



[m.'VECH 



or even more (table XIII). In an oak grove planted on the prairie 

 some 30 years before and sampled on practically the same dates 



TABLE XIII 



Moisture conditions in eastern Nebraska alfalfa field, adjacent to pr.a.irie 

 reported in table xii, showing failure of prairie veget.4.ti0n to reduce 



MOISTXIRE content OF DEEPER SUBSOIL NOT DUE TO ANY PECULIARITY OF SUBSOIL 



as the prairie fields, the subsoil moisture was found to be affected 

 to a greater depth than in the latter, the drying effect extending 

 apparently to at least 15 ft. (table XIV). 



TABLE XIV 

 Moisture conditions in an oak grov'e near Lincoln 



Discussion 



The moisture conditions in the deeper subsoil of the prairies 

 are very dissimilar according to whether we deal with humid or 

 with semi-arid fields. In the former at depths below 6 ft. the sub- 

 soil appears always moist, even after the severest drought, while in 

 the latter the extreme dryness indicated by ratios of i . o-i . 2 is 

 in general persistent in the deeper subsoil, extending to a depth of 



