PREFACE . 



THE object of the book is to provide a practical scientific 

 course in vegetable histology for the use of teachers and students 

 in schools and colleges. 



The medicinal plants are studied in great detail because 

 they constitute one of the most important groups of economic 

 plants. The cells found in these plants are typical of the cells 

 occurring in the vegetable Idngdom ; therefore the book should 

 prove a valuable text-book for all students of histology. 



The book contains much that is new. In Part II, which is 

 devoted largely to the study of cells and cell contents, is a new 

 scientific, yet practical, classification of cells and cell contents. 

 The author believes that his classification of bast fibres and 

 hairs will clear up much of the confusion that students have 

 experienced when studying these structures. 



The book is replete with illustrations, all of which are from 

 original drawings made by the author. As most of these illus- 

 trations are diagnostic of the plants in which they occur, they 

 will prove especially valuable as reference plates. 



The material of the book is the outgrowth of the experience 

 of the author in teaching histology at the College of Pharmacy 

 of the City of New York, Columbia University, and of years 

 of practical experience gained by examining powdered drugs in 

 the laboratory of a large importing and exporting wholesale 

 drug house. 



The author is indebted to Ernest Leitz and Bausch & 

 Lomb Optical Company for the use of cuts of microscopic 

 apparatus used in Part I of the book. 



The author also desires to express his appreciation to Pro- 

 fessor Walter S. Cameron, who has rendered him much valuable 



aid. 



WILLIAM MANSFIELD. 



COLUMBIA UNIVERSITY, 

 September, 1916. 



