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 with 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. 



