iv ~ PREFACE 
scheme is so elastic that no two classes need follow it in pre- 
cisely the same way; but may vary the work within wide 
limits, emphasizing now this aspect, now that, hurrying over 
one part and dwelling upon another as circumstances shall 
determine. The text printed in small type may be omitted 
with younger classes, or with those requiring only a short 
course. The matter in larger type will then be found to 
proceed connectedly, and to be in no way harmed by the 
omissions made. If a still shorter course be desired the class 
may go through as many topics as there is time for, leaving 
the rest to be taken up if possible at some future time. What- 
ever ground has been gone over, if well studied, will then be 
so much to the good; and since the educationally more im- 
portant subjects have been treated in the earlier chapters, 
the student may feel that even a little is worth while. 
The figures used in this book are mostly copies from 
various well-known works as indicated by the authors’ 
names in parenthesis under the figures; the remainder are 
from original drawings by the writer. Permission has been 
very kindly granted by Dr. N. L. Britton and Judge Addison 
Brown to use the figures from their Illustrated Flora. 
In conclusion, I wish to acknowledge most gratefully the 
helpful criticisms and suggestions received from teachers and 
other friends during the progress of the work. Especial 
thanks are due to Charles W. Swan, M. D., for suggestions 
regarding medicinal and poisonous plants; to Mr. Henry J. 
Williams, Mr. George W. Rolfe and Professor Kenneth L. 
Mark for help on chemical matters; to Professor G. H. 
Parker for reading evolutionary parts; to Mr. A. B. Seymour 
for reading the chapters on cryptogams; and to the botanists 
of the Harvard Herbarium and University Museum for 
facilitating my work with books and specimens. 
| gee Pies = 
CAMBRIDGE, MASSACHUSETTS 
December, 1912 
