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 thescience, 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. 
ul 
