PREFACE. 



The results described in the following pages were obtained by a 

 series of experimental observations begun in 1895 and continued 

 until the close of the year 1902. Originally designed to analyze the 

 phenomena of etiolation, the work has naturally led to a consider- 

 ation of the more general relations of the plant to light, and it is 

 believed that some important additions to the knowledge of the sub- 

 ject have been made. The chief results of value have been obtained 

 by long continued confinement of the etiolating plants in dark cham- 

 bers from which light was entirely excluded. 



The author has received material assistance from his students and 

 colleagues during the seven years over which the investigations 

 extended. The description of the etiolation of Oxalis and Sarrace- 

 nia ■purpurea is largely drawn from examinations of etiolated speci- 

 mens made by Mr. Wm. B. Stewart. A number of botanists have 

 rendered notable aid in the interpretation of some of the morpho- 

 logical facts presented. 



The illustrations are from drawings made from the actual objects 



or photographs, by Miss Alexandrina Taylor and Mr. August 



Mariolle. 



D. T. MacDougal. 



New York Botanical Garden, Jan. 10, 1903. 



