Botany 127 



No. 242. CLEMENTS, FREDERIC E. Plant Succession: An Analysis of the Devel- 

 opment of Vegetation. Octavo, xni+512 pages, 61 plates, SO figs. 

 Published 1916. Price $5.00. 



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 his- 

 torical, and brings together practically all the results so far obtained in the field. 

 The development 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, stabili- 

 zation and climax, structure and units of vegetation, direction of development 

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

 biotic forces which initiate succession, and of the processes, aggregation, migra- 

 tion, ecesis, competition and reaction, which carry it on. The relation of stabili- 

 zation to climax is discussed, and subclimax, preclimax, and postclimax are dis- 

 tinguished. Vegetation structures are interpreted as the outcome of develop- 

 ment, 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 analyzing the various views upon regression and retrogression, the conclu- 

 sion is reached that development is always progressive. 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 classification of seres or unit successions are examined, and a system is pro- 

 posed in which the climax is adopted as the primary criterion. Within each cli- 

 max, seres are distinguished as priseres and subseres with respect to the course 

 of development, and as hydroseres and xeroseres with reference to the initial 

 water-content of the bare area. 



The assumption is made that succession took place during the geological past 

 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 zooic evidences of them, climatic changes, climatic cycles, and the 

 correlation of cycles and succession. On the basis of climax vegetations, four 

 great eras are recognized, viz., Eophytic, Paleophytic, Mesophytic, and Cenophytic. 

 Successionally, each of these is characterized by an eosere, e.g., the Ceneosere, 

 while collectively, the four eoseres constitute the geosere, the total succession of 

 the geological past. The various kinds of cycles are dealt with at length, and a 

 tentative chart of them is constructed. The general principles of the phylogeny 

 and ontogeny of vegetation are formulated, and a somewhat detailed sketch is 

 given of succession during the Cenophytic and Mesophytic eras, and a general 

 account of the Paleophytic era. 



No. 290. CLEMENTS, FREDERIC E. Plant Indicators: The Relation of Plant Com- 

 munities to Conditions and Practices. Octavo. In press. 



This treatise is intended as a companion volume to "Plant Succession" and deals 

 with the value of climax and successional communities as indicators of factors, 

 processes, and practice. The analysis of the field falls into four general divisions, 

 viz., historical, bases and kinds of indicators, climax formations, and practice in- 

 dicators. The historical portion deals with the development of indicator ideals 



