ECEISiSN 



PLA 



BY 



DANIEL TREMBLY MACDOUGAL, Ph.D. 



Director of the Laboratories ^ New York Botanical Garden 

 Author of '^Practical Text-Book of Plant Physiology" 



WITH ONE HUNDRED AND EIGHT ILLUSTRATIONS 



LONGMANS, GREEN, AND CO. 



91 AND 93 FIFTH AVENUE, NEW YORK 



LONDON AND BOMBAY 



1902 



