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 ]\Ir. Henr}" 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. 



F. L. S. 

 Cambridge, Massachusetts 

 December, 1912 



