PREFACE 
SincE the last introduction to the study of sea- 
weeds was written, many years ago, the aspect of the 
whole subject has been completely changed by 
the progress of research. I have attempted in the 
following pages to keep the rule of describing only 
what I have personally verified by examination or 
by inspection of the original account, and this has 
been possible in nearly every case. 
It would have been more in accordance with 
usage to begin with the sub-class Rhodophycew, but 
I have permitted considerations of convenience to 
prevail. The Rhedophycee present so many diffi- 
culties, to be understood only after the study of 
other groups, that I have chosen Phwophycea, with 
its familiar forms of sea-wracks and tangles, for the 
first sub-class. The Chlorophycee and Diatomacew 
follow naturally. The &hodophycew next make a 
