PREFACE vii 



last but not least to Miss Gulielma Lister, who, many years 

 ago, showed me the winter-buds of the Frogbit in a pool in 

 Epping Forest, and awoke in me the desire to know more of 

 the ways of water plants. 



I have to thank the Councils of the Linnean Society, and 

 the Cambridge Philosophical Society, and the Editors of The 

 Annals of Botany^ The Journal of Botany^ and The American 

 Naturalist^ for permission to incorporate in this book parts of 

 the text and illustrations of certain of my papers which have 

 appeared in their publications. 



Of the figures in the present book, about one-third are 

 original; these are indicated by the initials A. A. The 

 sources of the others are acknowledged in the legends, but 

 I must take this opportunity of expressing my obligation to 

 the numerous authors from whose memoirs they are derived. 

 I am indebted to the Clarendon Press for the use of the block 

 for Fig. 127. The photographic reproduction of a number of 

 the illustrations has been carried out by Mr W. Tams, while 

 some have been re-drawn by Miss Evelyn M'^Lean. I have to 

 thank my sister. Miss Janet Robertson, for the design repro- 

 duced on the cover, which is based upon a wood-cut of the 

 Yellow Waterlily in Lobel's "Kruydtboeck," of 158 1. I am 

 much indebted to my father for reading and criticising my 

 manuscript and proofs. 



To my husband, E. A. Newell Arber, I owed the original 

 impulse to attempt the present study, which arose out of his 

 suggestion that life in Cambridge offered unique oppor- 

 tunities for the observation of river and fenland plants. To 

 his memory I dedicate this book. 



AGNES ARBER. 



Balfour Laboratory, 

 Cambridge. 



March i, 1920. 



