IV PREP A CE. 



longer be content with studying the various name-plates on 

 the machines ? 



For those who wish to follow the author's laboratory direc- 

 tions the placing of them after the paragraph or chapter to 

 which they are related may be a convenience. At least it 

 will emphasize the idea that this book is not intended to be 

 memorized and recited, but to serve as an explanation and 

 extension of knowledge acquired at first hand by the study 

 of plants. 



Teachers will find some suggestions which may be of ser- 

 vice in the use of this book in the preface to Plant Life. 

 The explanations and acknowledgments there made need 

 not be repeated here. 



C. R. B. 



The University of Chicago, 

 January 15, I900. 



