PREFACE. Vll 



Botany, to both of whom I desire to express my sincere 

 thanks. Dr Ellis not only undertook the chief part of the 

 drawings, but has also aided me in other ways in the 

 kindest manner. I am particularly indebted to him for 

 valuable help in the selection of laboratory material, and 

 for the arrangement of the Appendix containing instruc- 

 tions for practical work. 



To Mr Shipley, the Editor of the Cambridge Natural 

 Science Manuals, I am indebted for much kindly co- 

 operation. 



FRANCIS DARWIN. 



BOTANY SCHOOL, CAMBRIDGE. 

 January, 1910. 



