VI PREFACE. 



standpoint of the different members of the plant, their special 

 function and their special relations to environment. The stem, 

 root, leaf, flower, etc., are carefully examined and their ecological 

 relations pointed out. This together with the study of physiology 

 and representatives in the groups of plants forms a thorough 

 basis for pure plant ecology, or the special study of vegetation 

 in its relation to environment. 



Part IV. Vegetation in relation to environment. This part 

 deals with pure plant ecology in its general aspects, or vegetation 

 forms in relation to environment. First there is a study of the 

 factors of environment or ecological factors, which in general 

 are grouped under the physical, climatic, and biotic factors. 

 This is followed by the laws of migration, the analysis of vegeta- 

 tion forms and structures, plant formations and societies. Then 

 in order are treated forest societies, prairie societies, desert 

 societies, arctic and alpine societies, aquatic societies, and the 

 special societies of sandy, rocky, and marshy places. This 

 part closes with some practical suggestions for the study of plant 

 formations, and a description of the principal vegetation regions 

 of the earth. 



Part V. Representative families oj angiosperms. Topics for 

 study of additional examples of angiosperms are outlined here. 

 It is not intended that this shall follow Part IV in the course, 

 but where the teacher desires to study more examples than are 

 given in Part II these topics or chosen ones can be studied along 

 with or following Part III. The work of Part IV can usually 

 be well undertaken by field excursions in conjunction with the 

 work of Part III, and this would naturally be handled in the 

 spring, with Part I in the autumn and Part II in the winter. 



Acknowledgments. The author wishes to express his grate- 

 fulness to all those who have given aid in the preparation of this 

 work, or of the earlier editions of Elementary Botany; to his 

 associates, Dr. E. J. Durand, Dr. K. M. Wiegand, and Professor 

 W. W. Rowlee, of the botanical department, and to Professor 

 B. M. Duggar of the University of Missouri, Professor J. C. 

 Arthur of Purdue University, and Professor W. F. Ganong of 



