Pool: THE VEGETATION OF THE SANDHILLS OF NEBRASKA 213 



"standardized coated type" prepared after Livingston's directions 

 and sold by the Plant World. Distilled water was used throughout 

 the study and the several evaporimeters were frequently checked in 

 order that their readings might be compared. The evaporating 

 power of the air as determined by this method for six representa- 

 tive habitats, and also within the densest portion of the Jack Pine 

 plantations in the Dismal River National Forest, is compared in the 

 accompanying graphs, Fig. 7. This month was rather moister than 

 the usual summer months in the sandhills since the precipitation was 

 5.45 inches^ during the month. Probably, therefore, the evaporation 

 figures are quite low for the typical conditions. The data are to be 

 regarded as purely prehminary and may be of value with reference 

 to future data of the kind secured within the sandhills and the sur- 

 rounding territorv. These figures bring out striking differences in 



Fig. 8. Temperature map of Nebraska. The isotherms show the mean annual tempera- 

 ture in degrees F. (From Warren.) 



the evaporating power of the air in different situations, as for 

 instance that of the open hilltop is more than twice that of a pro- 

 tected basin or pocket only a few hundred yards away. The satura- 

 tion deficit and the temperature of both air and soil would also be 

 expected to vary considerably through the different habitats. This 

 has also been demonstrated in a preliminary manner. Briggs and 

 Belz (19) give 41.3 inches as the average evaporation (from an 

 open tank) at North Platte, Nebraska, near the southern margin 

 of the sandhill region, for the summers (April to October) 1907 to 

 1909 inclusive, while at Lincoln the average for eleven years has 

 been 34.8 inches. 



A glance at the accompanying map (Fig. 8) will show that the 



1 From the official records of the Forest Service, Halsey, Neb., 1911. 



