PREFACE vn 



its later development, however, it has contributed so many 

 important data essential in any discussion of phylogeny that 

 we have asked Professor E. C. Jeffrey to present the general 

 outlines of the subject in the last two chapters of this volume, 

 a discussion which includes both Gymnosperms and Angio- 

 sperms. It is hoped that this presentation will help to stimu- 

 late the cultivation of an important field of research too much 

 neglected in this country. 



It did not seem necessary to treat the two great groups of 

 Angiosperms separately. They are so similar in their essential 

 morphological features that their separate presentation would 

 have involved a needless amount of repetition. We have also 

 continued to regard the spore mother-cell as the end of the 

 sporophytic generation, and its division as the beginning of the 

 gametophyte. The reasons for this are more fully presented 

 in the present volume than in the preceding. 



In the chapters upon classification we have presented the 

 scheme elaborated by Professor Engler, believing that it is 

 the best expression of current knowledge of relationship ap- 

 plied to the whole group, and that it is suggestive of the most 

 critical regions for research. This has not been pressed to the 

 dreary details of minor groups, for these are easily accessible. 

 It has rather been our intention to present the general ideas 

 involved in the alliances of first rank, so that principles rather 

 than details may be prominent. We have also thought that 

 the special student should be somewhat familiar with the his- 

 tory of the group, so far as known, its geographic distribution, 

 and the current notions as to its phylogeny. The last subject 

 may be regarded as more theoretical than profitable, but the 

 final aim of morphology is a definite phylogeny. and advance 

 toward it must be made by a succession of theoretical con- 

 clusions. 



Johx M. Coulter. 



Charles J. Chamberlain. 

 The University ok Chicago, 

 January, 1903. 



