394 Floristik, Geographie, Systematik etc. 



Clements, F. E., Plant Succession: An Analysis of the 

 Development ofVegetation. (Carnegie Instit. of Washington. 

 (Publ. 242. XIII, 512 pp. 61 pl. 51 text fig. Washington 1916.) 



This treatise is an endeavor to give a complete account of the 

 development of Vegetation and to lay down the basic procedure 

 upon which future research must rest. The analysis falls into three 

 general divisions. One of these is historical, and brings together 

 practically all the results so far obtained in the field. The develop- 

 ment of successional ideas is traced by an analysis of major con- 

 tributions from the seventeenth Century to the present. For North 

 America abstracts are given of all the works upon succession, and 

 these are arranged under the various climaxes and seres. 



The studies of European succession are summarized by regions, 

 while a special section is devoted to investigations of peat horizons. 

 A consistent attempt is made to take into account all existing 

 results and interpretations, A Chapter is devoted to the quadrat 

 and instrument methods which are regarded as indispensable to 

 adequate research, 



The treatment of present-day succession falls under several 

 heads, namely, concept and causes of succession, initial causes, 

 ecesic causes, reactions, stabilization and climax, structure and 

 Units of Vegetation, direction of development and Classification ot 

 seres. An account is given of the topographic, climatic and biotic 

 forces which initiate succession, and of the processes, aggregation, 

 migration, ecesis, competition, and reaction, which carry it on. 



The relation of stabilization to climax is discussed, and subcli- 

 max, preclimax, and postclimax are distinguished. Vegetation struc- 

 tures are interpreted as the outcome of development, and hence as 

 universal evidences of it. The concept of the formation is made as 

 objective as possible by basing it wholly upon development. As a 

 result, each climax becomes a formation, in which it is necessary 

 to recognize certain climax units, association, consociation and 

 Society, and developmental ones, associes, consocies and socies. 



In anah^zing the various views upon regression and retrogres- 

 sion, the conclusion is reached that development is always progres- 

 sive. Regression is only the halting of succession in consequence 

 of partial or complete denudation, followed by the resumption of 

 the normal progressive movement. The various bases for the Clas- 

 sification of seres or unit successions are examined, and a sjJ'Stem 

 is proposed in which the climax is adopted as the primary criterion. 

 Within each climax, seres are distinguished as priseres and sub- 

 seres with respect to the course of development, and as hydroseres 

 and xeroseres with reference to the initial watercontent of the 

 barea area. 



The assumption is made that succession took place during the 

 geologic part essentially as at present, and the field of paleo-ecology 

 is organized upon this basis. In the discussion of past climates and 

 climaxes, an account is given of Vegetation eras, the plant record, 

 deformation and gradation, past climates, with geologic, botanic and 

 Zoologie evidences of them , climatic changes, climatic cycles, and 

 the correlation of cycles and succession. On the basis of climax vege- 

 tations, four great eras are recognized, viz., Eophytic, Paleophytic, 

 Mesophytic, and Cenophytic. Successionally, each of these is cha- 

 racterized by an eosere, e.g., the Ceneosere, while collectively, the 

 four eoseres constitute the geosere, the total succession of the geo- 

 logic past. The various kinds of cycles are dealt with at length. 



