April, 1903 .] 
Memoir on Etiolation Studies. 
4i5 
AN AMERICAN MEMOIR ON ETIOLATION 
STUDIES. 
A. D. Selby. 
MacDougal, Daniel Trembly. Ph D. "The Influence of Light and Darkness Upon 
Growth and Development." Memoirs of the New York Botanical Garden, Vol. II, pp. 
XIII and 31!!, with 174 figures in the text. New York, 1903, published by the Garden by 
the aid of the David Lydig Fund. 
In the latest volume of the Memoirs of the New York Botanical 
Garden, Dr. MacDougal publishes the results of experimental 
observations on etiolation, begun in 1895 and continued till the 
close of 1902. Those from 1895 to 1899 were made at the Uni- 
versity of Minnesota in portable dark chambers; from 1899 to 
1902 in a specially constructed dark chamber in the Museum 
Building of the New York Botanical Garden. Ninety-seven spe- 
cies belonging to diverse classes have been cultivated in continuous 
darkness with control plants in the ordinary alternation of day- 
light and night. The species studied include “aquatics, creepers, 
climbers, succulents, mycorrhizal forms, geophilous plants and 
aerial shoots, mesophytes, and spiny xerophytes.’’ These consti- 
tute the most comprehensive series of etiolation studies ever 
undertaken by a single individual, so far as known to the writer. 
The details with respect to the several species are presented 011 
pages 35 to 200, preceded by a historical resume of described 
etiolation phenomena from Ray (1686) and Hales (1727) to the 
present day, and followed by discussion of the various features of 
the results, covering 109 pages ; also an excellent index. 
One result of Dr. MacDougal’s investigations has been to show 
the error of earlier investigators who attributed to light a retard- 
ing effect upon growth. His results have also contributed to the 
complexity of the phenomena. Many other of the older generali- 
zations aside from the one already named must be modified in the 
light of his researches. It has been found that a large number 
of herbaceous biennials and perennials do not show an excessive 
elongation of the stems or shoots in darkness. To these belong 
Aster divaricafus , Cypripedium montanum , Galium circaezans , 
Ipomcea batatas, Phytolacca decandra , Saururus cernuus and Vag- 
nera ste/lata. 
The effect of etiolation upon leaves is treated under the follow- 
ing heads : 
Sterile and spore-bearing leaves of pteridophytes. 
Etiolation of leaves of monocotyledons with parallel venation. 
Etiolation of petiolate leaves of monoctyledons with open or 
reticulated venation. 
Etiolation of leaves of dicotyledons arising from subterranean 
stems or bulbs. 
Leaves of dicotyledons arising from aerial stems. 
