VIU AUTHOR S PREFACK. 



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 ia 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 unpuhlished 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. 



