ECOLOGICAL SUCCESSION. 



81 



in October when it falls below that of the oak dunes and is even 

 less than that of the beech maple forest. This would give good 

 reasons for expecting to find within this association truly meso- 

 phytic plants whose activities are limited to the early spring. 







Cottonwood dune 

 Pine dune 

 Oak dune 



Oak-hickory forest 

 Beech-maple forest 



FIG. 3. Showing the comparative evaporation rates (cc. per day) in the ground 

 stratum of the different animal communities from May to October. (Courtesy of 

 Mr. G. D. Fuller.) 



Evaporation in the various associations varies directly with the 

 order of their occurrence in the succession (Figs. 3, 4). The 

 differences in the rate of evaporation in the various plant asso- 







10 



Cottonwood dune 

 Pine dune 

 Oak dune 

 Beech-maple forest 



FIG. 4. Showing the comparative evaporation rates (cc. per day) in four of the 

 animal communities on the basis of the maximum amount per day for any week 

 from May to Oct. (Courtesy of Mr. G. D. Fuller and the Botanical Gazette.} 



ciations studied are sufficient to indicate that the atmospheric 

 conditions are most efficient factors in causing succession." (Ful- 

 ler, 'ii.) 



A comparison of Fuller's data with the tables and lists of 

 animals shows that the distribution and succession of animals 

 is clearly correlated with the evaporating power of the air. Further 

 comparison with the description of stations (p. 6l) shows that 

 the evaporating power of the air may be taken, in this case, as 

 an index of the materials for abode, etc. 



