Vlll AUTHOR S PREFACE. 



fruitless, has afforded a practical demonstration of the 

 need of some system for the centralization and cataloguing 

 of all specimens, which have served for the diagnosis or 

 illustration of new species. 



I desire to convey my hearty thanks to those in charge 

 of the museums I have visited for their kindness in affording 

 me every facility in the examination of collections, and for 

 their willingness to assist my work in various ways. Among 

 continental friends who have aided me I wish to express 

 my gratitude to Professor Nathorst, who generously placed 

 at my disposal some unpublished drawings of specimens 

 collected by himself ; also to Dr. Renault and Professor 

 Zeiller, of Paris, who enabled me to obtain access to the 

 Jurassic plants under their charge. 



My thanks are due to Miss Woodward for the care with 

 which she has executed the drawings published in this 

 volume ; to my wife I am also indebted for some of the 

 drawings reproduced in the text, which were made from 

 specimens in the museums of Whitby, Scarborough, and 

 York. The photograph reproduced in Text-figure 34 was 

 kindly taken for me by Mr. Gepp, of the Botanical 

 Department. 



The Councils of the Royal Society and the Literary and 

 Philosophical Society of Manchester have allowed me to 

 borrow process-blocks originally used in their publications, 

 and the Syndics of the Cambridge University Press 

 generously gave me permission to use several blocks in 



their possession. 



A. C. SEWARD. 



EMMANUEL COLLEGE, CAMBRIDGE. 

 November 20, 1900. 



