358 BOOKS AND CURRENT LITERATURE 



Fuller has made several studies of the relation between evaporation 

 and plant communities, but only two of these deal directly with suc- 

 cession. In Evaporation and Plant Succession, "^ his major conclusion 

 is that "The differences in the rates of evaporation in the various plant 

 associations studied are sufficient to indicate that the atmospheric 

 conditions are efficient factors in causing successions^ It seems signifi- 

 cant that the final comprehensive paper is entitled "Evaporation and 

 soil moisture in relation to the succession of plant associations."'* The 

 conflict in opinions can be traced directly to the statement that "The 

 evaporation thus controlled and changed is one of the principal factors 

 in causing the development of a different vegetation, or in other words, 

 the decreased rate of evaporation caused by the heavier vegetation is 

 the direct cause of succession between different associations" (p. 199). 

 The latter part of this statement would seem to be a slip of the pen if 

 one may judge from the evidence afforded by the general conclusions 

 and summary. "The progressive increase in the water-retaining power 

 of the soil, due largely to its increased humus content, must play no 

 inconsiderable role in causing the succession here culminating in the 

 mesophytic beech-maple forest" (p. 231). "T/iese comparative values 

 of the moisture factors [ratios between evaporation and available water] 

 show such a surprising rate of increase as one proceeds from the pioneer 

 to the climax associations that it cannot be doubted that such a change 

 in water conditions must be one of the chief factors, if not the most 

 important cause, of the succession of associations from the more xero- 

 phytj^ to the more mesophytic" (p. 231). ''The evaporation rates and 

 the amount of growth-water in the various associations vary directly 

 with the order of their occurrence iii the succession, the pioneer being 

 the most xerophytic in both respects. The ratios between evaporation 

 and growth-water in the beech-maple forest, oak-hickory forest, oak 

 dune, pine dune and cottonwood dune associations have been shown to 

 have comparative values. of 100, 65, 20, 17 and 15 respectively, and the 

 differences thus indicated are sufficient to be efficient factors in causing 

 succession." 



Gleason and Gates,^ working in the same general region as Fuller, 



2 Fuller, G. D. Evaporation and Plant Succession. Bot. Gaz. 52: 193. 1911. 



3 The italics here and later are the reviewer's. 



* Fuller, G. D. Evaporation and Soil Moisture in Relation to the Succession 

 of Plant Associations. Bot. Gaz. 58: 193. 1914. 



^ Gleason, H. A. and Gates, F. C. A Comparison of the Rates of Evaporation 

 in Certain Associations in Central Illinois. Bot. Gaz. 53: 478. 1912. 



