PREFACE ix 



Wise Suilon for some of the drawings. Mr. Alban Stewart jjre- 

 pared the camera lucida drawings of tissues of Aviccnnia. Psidium 

 and Mangrove, from materials collected by him in ihe Oalapogos 

 Islands. Mr. L. M. Peace made the jjliotomicrographs appearing 

 here, prepared many of the sections from which the drawings 

 were made, and gave me many valuable suggestions for the 

 chapters on microlechnic. 



My thanks are due my colleagues, Dr. M. A. Barber, Dr. C. E. 

 McClung, Dr. V. II. Hillings, and Prof. Chas. M. Sterling for 

 reading and critizing different parts of the ])ook. and to Ada 

 Pugh Stevens for reading all of the j^roof sheets. 



W. C. Stevens. 



Umversitv of Kaxsas. 



