DISCUSSION OF ECOLOGICAL FACTORS 49 



the last to recover from a state of winter; their conditions 

 favoring growth are retarded more by north winds and ac- 

 celerated less by south winds than those of any other ex- 

 posure. It is not surprising, then, that we find their pre- 

 vernal and vernal bloomers 7-17 days behind those of 

 southern exposures. The soil of crests and steep, exposed 

 slopes of ridges contains the least amount of water-content 

 on account of excessive drainage and evaporation; that of 

 draws and meadow formations the largest amount. Other 

 things being equal, northern exjwsures lead all others in 

 water-content. The more extensive vegetative covering of 

 the meadow formations as compared with that of the ridges 

 will undoubtedly exert some influence upon soil temperatures 

 and water-content. 



The soil about Nebraska City is largely of glacial origin 

 overlaid with a rich deposit of loess. It is very porous, dark- 

 gray in color, and of a light, pulverulent, uniform texture, 

 particularly rich in organic matter and potash. The general 

 physical properties of the soil correspond with the character- 

 istics of sandy loam. Porous soil, especially when sandy, 

 has a great capacity for water and air. The water falling 

 upon the surface will largely be absorbed, the water-content 

 of the soil will be accordingly increased, thus reacting upon 

 the floral covering, and erosion will be reduced to a minimum. 

 It is estimated that at least 90 per cent of all water falling 

 upon this soil is absorbed. 



Through the courtesy of J. Sterling Morton, under v/hose 

 direction the work was carried on, we are permitted to pub- 

 lish the following chemical analysis of soil collected about 

 Nebraska City, made in 1873 by Charles A. Goessmann, Pro- 

 fessor of Chemistry, Massachusetts Agricultural College. 

 "The soil lost, when kept over dry calcium chloride, 1.6 per 

 cent of water ; it absorbed, in an air saturated with moisture 

 at 56° F., 5.04 per cent of moisture; when dried at 212° F., 

 it lost 4.05 per cent of moisture; upon being calcined, it lost 



