Vlll PREFACE 



the student interested at the very outset in scientific 

 method, and to lead him to see that this method may be 

 of great value to him in life as well as in the laboratory. 

 Trial of this introduction has indicated that more of in- 

 terest and effort is aroused when such material is included 

 than when it is omitted. Many teachers have been inter- 

 viewed as to their opinion of such an introduction. It is 

 evident that the idea meets with approval, whatever opinion 

 may prove to be as to the manner in which it is carried 

 out in this book. If the introduction is used as lessons, it 

 should be used before laboratory work is begun. 



Maintenance of Effort. Just so far as is practicable, 

 the familiar always precedes the unfamiliar in the sequence 

 of topics. With a view to maintenance of effort as well as 

 of interest, the amount of " resistance " is gradually in- 

 creased as the reader progresses. Thus the technical 

 discussion of foods is postponed until Chapter IX, while 

 the non-seed plants, and the " hidden " parts of seed 

 plants, are discussed in the last two chapters. Yet these 

 two chapters, if what comes before is well understood, 

 need be no more difficult than the earlier chapters. Alter- 

 nation of generations and the morphological nature of 

 seeds are not topics intrinsically difficult. Only their 

 unfamiliarity makes them seem difficult. The exclusion 

 of these topics is warranted only by a teacher's inability 

 to present them clearly. Their inclusion is warranted by 

 their necessity to even the most elementary conception of 

 plant evolution, and by the need of them in any adequate 

 conception of seed plants themselves. 



Plan of Presentation. The plan of presentation is, in 

 a limited sense, spiral. Chapters I and II give a general 

 view of a seed plant as a whole. Chapters III to VIII 

 are devoted to an expanded treatment of what is briefly 



