EVAPORATION AT SKOKIE MARSH 



157 



number of cubic centimeters of water lost per day by a standard 

 atmometer, while the abscissae represent the intervals between 

 the weekly readings. 



A study of figure 2 shows the periods of maximum and mini- 

 mum evaporation to have been fairly harmonious at the four 

 stations. And again, the evaporation rate for the center of the 

 reed swamp (figure 2, a), where hydrophytism is greatest, was 

 usually lowest; in the swamp meadow (fig. 2,c), it was somewhat, 

 higher; in the outer part of the reed swamp (fig. 2,6), still higher. 



MAY 



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Fig. 2. Average daily evaporation rates in o, center of reed swamp; h, outer 

 part of reed swamp; c, swamp meadow, and d, forest. 



and in the Quercus bicolor-Fraxinus americana or swamp white 

 oak-white ash forest (fig.2,d), it was highest of all. These differ- 

 ences become perhaps even more visible if we compare the aver- 

 age daily evaporation amount at each station for the entire period 

 of 147 days; viz., a, 3 cc; c, 4.27 cc; 6, 4.5 cc, and d, 7.91 cc. 

 Or, taking the rate for d as 100 %, then the rate for a was 38 %; 

 for c, 54 %, and for h, 57 %. Expressed in general terms, the 

 evaporation rates were inversely proportionate to the hydro- 

 phytism of the station. This is due chiefly to the greater amount 



