PREFACE vii 



I wish to thank Sir David Prain and the staff at Kew, more 

 especially Drs Hill, Stapf, and Rolfe, and Mr S. A. Skan, 

 whose detailed knowledge of the library has been of the 

 very greatest assistance in easing my labour. The writing 

 of this edition has occupied very much time during the last 

 five years, and I am particularly grateful to Prof. Seward, 

 who placed at my disposal a table large enough to enable 

 me to spread out 20 works of reference at once, and to 

 Dr Moss and others of the Cambridge staff. The first two 

 of the five years were spent in Rio de Janeiro and I am 

 much indebted for help to my colleagues there, particu- 

 larly the late Dr Alberto Lofgren and Dr Achilles de Faria 

 Lisboa. I also owe many useful suggestions to my col- 

 leagues in other Botanic Gardens, e.g. Prof. O. Ames at 

 Harvard, Prof. I. B. Balfour at Edinburgh, Prof. N. L. Brit- 

 ton at New York, Mr I. H. Burkill at Singapore, Prof. A. 

 Engler at Berlin, Dr J. H. Maiden at Sydney, the late Dr 

 H. H. W. Pearson at Cape Town, Dr Sargant at Jamaica Plain, 

 and others. The late Dr E. A. N. Arber, and Mrs Arber, 

 have laid me under very many obligations, and so have 

 Sir Francis Darwin, Professors Bower, Farmer, Goebel, 

 Goodale, Henry, Lang, Oliver, Scott, and Yapp, and Messrs 

 Davie, Lock, Lynch, Riddle, Small, Smith, and many more. 

 To my wife my obligations are unmeasured. Finally for the 

 illustrations I have to thank Herr Engelrnann for permis- 

 sion to copy some of the late Prof. Eichler's figures, and 

 Dr Rendle for the use of some of those in his book on 

 Classification. 



J. C. WILLIS. 



CAMBRIDGE, 



April 4, 1919. 



