ACKNOWLEDGMENTS XIX 



graphic prints made for the late Professor Wilham H. Brown's The 

 Plant Kingdom, pubhshed in 1935. This was not only a great 

 convenience but also a great privilege, these illustrations being often 

 of unsurpassed excellence. Acknowledgment is also due to the 

 National Museum of Canada for permission to reproduce many of 

 my photographs of arctic regions that are now in their possession. 

 Other sources of illustrations, where not contributed by myself, are 

 acknowledged individually. 



Nicholas Polunin 

 Faculty of Science, 



Baghdad, Iraq 

 Spring, 1957 1 



^ Since this was written it has not been possible to incorporate extensively any 

 new ideas or to consider subsequent works, though some details of publication 

 have been brought up to date. The proofs have kindly been read by Professor 

 John H. Burnett and Dr. A. D. Q. Agnew (now of my Department in Baghdad), 

 while in connection with their correction warm thanks are due to my secretary, 

 Miss Christine Wright. Acknowledgment is also made to Dr. B. Barnes for his 

 valued part in the preparation of the Index. 



