AtTTHORS PRBFAOE. Ml 



original description. Now, in my list, this species appears 

 under Aspidium, with a remark that it was re-named by 

 Knowlton Dryopteris ; but it ig not entered again by me under 

 Dryopteris. On the other hand, various species similaily 

 treated by Knowlton and others do find their place in my list 

 under two or even more genera : in most cases this depends on 

 the fact that where I have found a name used in the general 

 literature, or where for some reason it appeared useful to have 

 the different references to the plant, 1 have added it to my list. 



Even after the list was restricted in this fashion, it proved so 

 bulky that only the Thaliophita could be dealt with critically 

 in the present volume. Other portions of the Cretaceous Flora 

 will be considered as is convenient in future volumes. 



It is certain that there are many errors in this work, though 

 I have laboured to avoid them. Those who have done any 

 task of the kind will realise how difficult it is to deal with such 

 enormous numbers of references, particularly when parts of the 

 text have to be printed oflF before the later sections are revised. 



In the course of the preparatory work I have travelled much, 

 and though much of the help here mentioned will not bear fruit 

 till the future volumes are completed, I should like to say here 

 how greatly I am indebted to friends and officials for help in 

 the work and for facilities for examining specimens in numerous 

 museums on the Continent and in America. Above all I must 

 thank Mr. W. E. Balston and the Government Grant Committee 

 of the Pioyal Society of London, for grants partially to defray 

 the cost of these journeys. 



Among so many who have rendered assistance in various 

 forms, it seems invidious to single out persons for special 

 thanks, but mention must be made of the kindness of the 

 authorities and staff of the National Museum in Washington, 

 where I had the advantage not only of examining many 

 type-specimens, but also of comparing their bibliographic slips 

 with mine, whereby I gained many additions to my lists. 

 Prof. Nathorst has been most helpful both when on his visits 

 to London and in Stockholm, where he placed the remarkable 



