PREFACE v 



Valuable suggestions from many teachers and students of 

 botany have been gladly received, and these will doubtless serve 

 to render the book more helpful and usable than it otherwise 

 would have been. Especial thanks are due to Dr. Norman 

 MacLeod Harris of the Department of Bacteriology of The 

 University of Chicago, who has read the chapter on bacteria ; 

 and to Mr. William L. Eikenberry of the University High 

 School, Chicago, who by his frequent suggestions, based 

 on extensive experience, has been constantly helpful in the 

 preparation of this book. 



JOSEPH Y. BERGEN 

 OTIS W. CALUWELL 



