X 
PREFACE TO THE SECOND EDITION 
the topics included in these might be mentioned a treatise on Cell 
Formation and Reproduction including Indirect Nuclear Division, 
twenty pages on Non-Protoplasmic Cell Contents, the considera¬ 
tion of Woods, Root Tubercles, the gross structure and histology of 
different types of leaves, broad histologic differences between Mono- 
cotyl and Dicotyl leaves, the histology of floral parts and the his¬ 
tology of types of fruits and seeds. Chapter VIII on Taxonomy 
has been increased by the addition of 144 pages. Several new fami¬ 
lies of drug-yielding plants have been added and the treatment of 
family characteristics has in the majority of instances been broad¬ 
ened. The habitats of drug-yielding plants have been added. In 
that portion of the tables dealing with the names of official drugs, 
those official in the National Formulary have been so designated by 
the abbreviation N. F., to distinguish them from others that may 
occur in the same portion of the table and which are official in the 
Pharmacopoeia. 
In keeping \vith the increased size of the book, many new illus¬ 
trations have been introduced. A number of these are original 
drawings, photographs and photomicrographs. To the authors of 
other works from which cuts were borrowed, the writer’s thanks are 
due. 
The writer in conclusion desires to thank Dr. John M. Macfarlane, 
head of the Botanical Department of the University of Pennsylvania, 
for valuable suggestions during the preparation of portions of the 
text. 
H. W. Y. 
