PREFACE 



In offering this book to college teachers it may not be 

 amiss to refer to the great change that has taken place 

 in the teaching of Botany in America since the prepara- 

 tion of its predecessor thirty-five years ago. Then 

 botanical laboratories were just coming into existence, 

 and for the first time students of Botany were able 

 to study protoplasm and cells and tissues and other 

 minute structures of plants. It is a matter of history 

 that half a dozen years later the publisher's objection 

 to the caption "Laboratory Studies" for a new edition, 

 was able to bring about the substitution of "Practical 

 Studies," as less likely to prejudice teachers against such 

 presentation of the subject. Looking back to that time 

 we realize what progress has been made in the teaching 

 of the science, for to-day every college- has its laboratory for 

 the study of plant structure, and this change in teaching 

 has gone so far that it has invaded the secondary schools, 

 in which there are now many well-equipped botanical 

 laboratories. 



Looking at the science from another standpoint it is 

 of interest to note that thirty-five years ago the number 

 of species of known plants was between 125,000 and 

 150,000, while to-day it has risen to more than 233,000. 

 Then the number of flowering plants was placed at a 

 little more than 100,000, while now it is about 133,000: 

 then the lower plants ("cryptogams") were thought to 

 number from 25,000 to 40,000, while now there are 

 more than 100,000 enumerated. 



