BOOKS AND CURRENT LITERATURE 



Recent Investigations on Evaporation and Succession. — 

 The appearance of Gates's paper on "The relation between evaporation 

 and plant succession in a given area" has suggested the desirability 

 of examining the conflicting \aews in this field. This task is made 

 easier by the facts that methods and results are essentially in accord 

 throughout. The divergence in the several investigations is limited 

 to the conclusions drawn as to the role of evaporation, and it centers 

 around the question whether evaporation is a cause or an effect. Fuller 

 and Weaver regard evaporation as essentially causal to succession, a 

 view which seems to be shared by Transeau in some degree. On the 

 other hand, Gleason and Gates consider it merely a consequence of the 

 increasing population and the resulting shade. A careful examination 

 of their conclusions readily discloses the source of the disagreement, 

 and serves to harmonize the results more or less completely. 



Transeau^ was not especially concerned with the dominants of the 

 various communities, and his results do not bear directly upon the serai 

 movement. Moreover, it cannot be said with certainty that he regards 

 evaporation as causal, though the following statements seem to indi- 

 cate this. "With these data in hand it is not difficult to see why 

 seedlings of Trillium, Arisaema and Veratrum are successful in the 

 swamp forest with its 10% relative evaporation; why they fail in the 

 open hillside forest with its 50% rate; and why they are never seen 

 on the near-by gravel slide with its relatives rate of 100% in addition 

 to its unstable character." 



"In the reforestation of the gravel slides in this locality it vdW be seen 

 that the greatest decrease in the demands for transpiration on the 

 part of seedlings takes place during the first stages. This greatly aids 

 in accounting for the well-known fact that development toward a 

 closed association proceeds with such increasing rapidity when once a 

 few plants gain a foothold. Attention has been frequently called to 

 the importance of pioneers as shade producers, while their effective- 

 ness in reducing transpiration has been underestimated." 



1 Transeau, E. X. The Relation of Plant Societies to Evaporation. Bot. 

 Gaz. 45: 217. 1908 



357 



THE PLANT WORLD, VOL. 20, NO. 11 



