viii PREFACE 



ing this preliminary background. For that reason we have included in 

 the textbook numerous discussions of various kinds of interrelations 

 for further consideration outside of class. 



Botany is primarily a concrete science and is most effectively ap- 

 proached through a first-hand study of plants. We have found class 

 discussions while observations are being made a most satisfactory 

 approach. A workbook is available as a convenient aid in some of the 

 class periods and as a means of further suggestions for work outside 

 class periods. The textbook has been written primarily to supplement 

 what is observed and discussed. It is intended to help students review, 

 organize, amplify, and correct their own observations, inferences, and 

 ideas, whether they obtained them first-hand or by hearsay. We have 

 tried to interfere as little as possible with the teacher who prefers to 

 have students observe and discuss plant phenomena before books are 

 consulted. Nearly every chapter has been written with the assumption 

 that it will not be read by the student until the instructor thinks that 

 the student's own observations should be supplemented by what is 

 written. The sequence of topics within a chapter is not always the 

 best one to follow in observation and oral discussion. 



Since there is no fixed standard of knowledge and procedure that 

 one may rely upon indefinitelv and in all circumstances, we have tried 

 to present a cross section of what appears to us to be in keeping 

 with the immediate present. We believe that there is a body of basic 

 information, scientific inferences, and points of view about the plant 

 part of our environment that is as important a background for students 

 who intend to major in any phase of plant science as it is for that much 

 larger group of students who are taking the course in botany as part 

 of their general education. Our aim has been to help the students 

 organize that background and appreciate some of the numerous inter- 

 relations of plants and of plants and animals, particularly man. It is 

 of course impossible to incorporate in a book of this size all the informa- 

 tion demanded by students while they are comparing observations and 

 inferences. Furthermore, some of the information needed is best sup- 

 plied by the teacher, either directly or through the assignment of 

 specific observations or references. 



The general course may begin at different seasons of the year, when 

 readily available plant materials may differ greatly. For that reason 

 the first five chapters contain discussions of materials which are useful 

 in approaching the study of plants under different conditions. As the 



