PREPAGE. 
WuiLE embodying in this book the results which 
I have accumulated during the past twenty years, 
I should like to take the opportunity of thanking 
the many friends who have assisted me. The 
first to do so were Mr. Carruthers and Professor 
A. G. Nathorst, whose work, in fact, led me to 
undertake these studies. In the troublesome work 
of determining the plants I have been greatly aided 
by the constant courtesy and assistance of the 
officers of the Botanical Department of the British 
Museum, especially of my friends Mr. E. G. Baker 
and Mr. A. B. Rendle. At Kew also I have 
received every facility for the work, and to Mr. 
J. G. Baker, the late keeper of the Herbarium, | 
owe much. Messrs. G. and H. Groves have also 
assisted me at various times with specimens of 
recent plants which I was unable to obtain for 
myself, and others have been received from 
‘friends whose names are too numerous to mention. 
With regard to the geological material that I 
have obtained from others, specimens have been 
