48 BOOKS AND CURRENT LITERATURE 



sions should form the basis of instrumental study. This is especially 

 true of those paragraphs dealing with water relations. Very few 

 studies have been made which in any adequate way touch the moisture 

 problem. The soil sampling systems employed are not extensive 

 enough to afford more than superficial indications of the real moisture 

 conditions under which plants grow. The moisture consumption of 

 native plants is unknown and often the measurements recorded give 

 no indication of the total amount of water available for growth. It 

 is true the vegetation is in some ways the best indication of moisture 

 conditions, but to interpret soil moisture conditions on the basis of 

 vegetation and the vegetation on the basis of the inferred moisture con- 

 ditions is a decidedly observational method. Moisture conditions can- 

 not be studied without an equipment and amount of labor seldom sup- 

 plied, but they are none the less essential to an interpretatioli of vege- 

 tation. A careful perusal of this portion of the book should suggest 

 at once a score of unsolved problems, many of which are of profound 

 importance in the study of vegetation. 



Under stabilization and climax, the author emphasizes the conclu- 

 sion that progressive invasion typical of succession everywhere re- 

 sults in stabilization. Stabilization is an increase in dominance and 

 culminates in a climax. Both climax and development units of vege- 

 tation are considered and a system of classification proposed. In the 

 brief historical summary the terms "formation" and "association" 

 are discussed but the concepts involved by different authors in the use 

 of these terms are not considered as seriously as colild be desired. In 

 the early stages of the development of any science the same terms may 

 be used to signify now one thing and now another. Concepts are more 

 important than terms and in the discussion of the association it is 

 more important that the vegetation unit involved in the discussion be 

 considered than that the term which was applied to this imit conform 

 to present day usage. 



The author has swung largely from the habitat basis to the develop- 

 ment basis in this book, but the development basis is founded clearly- 

 o:> f.v^ristics and habitat. By using development it is possible to in- 

 clude in tne formation distinctive outstanding communities such as 

 grass and forest communities. Still the habitat is really the basis of 

 the formation, although the climate is indicated by the vegetation. 

 Up to the present the vegetation cannot be predicated from climatic 

 data with the desired degree of certainty. 



