,90,1 OLSSON-SEFFER-VEGETATION ON SEA SHORES 95 



have treated this subject in another place (12). With regard to the 



pt 



vailed. 



m 



1m 



theory which gives to the physical properties of the soil the largest 

 bearing. Since the physical conditions 



main 



W 



ixg, hold that these are of greater consequence. 



In discussing the physical conditions of sand formations we w 



ill 



temperatures 



measurements 



the writer. 



Soil temperature.— The heat-absorbing power of sand is low in 

 comparison with other darker-colored soils, but because the radia- 

 tion is great the vegetation on a surface of sand is subjected to a com- 

 paratively high temperature. As the sand is always moist only a 

 little below the surface the heated layer of sand does not reach deep 



temperat 



moist 



Part of the root is under the influence of the heat of the surface 

 stratum of sand. We find corresponding adaptational protections 

 on the roots of most plants growing in sandy soils. 



The transport of heat within the soil is influenced by several factors 



one laver to another. It is impossible, 



from 



eliminate 



movements of water and air in the soil, the evaporation of water from 



the 



warmer 



Th e data here supplied therefore represent the temperature of the 

 soil under conditions such as it presents in the field. 



In a11 observations made by the author ordinary soil thermometers 

 Were used > and the temperature was taken at following depths: 2, 5, 



I0 > 20, and 5o cm . 

 in loo 



instrument 



loose sand at the desired depth. The number of complete series 

 ohs ervations made on different sand formations reaches 876. Some 

 °t these will here be referred to, and in other cases average values 



Will K« -!— ' 





0n the front beach the temperature of the soil is varying more 



