April, 1903.] Memoir on Etiolation Studies. 415 



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. 11, pp. 

 XIII and 319, with 174 figures in the te.xt. 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, m3'corrhizal 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 on 

 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 

 As^er divaricafiis, Cypripediian luoitaiiuiii, Galium circaezans, 

 Iponnra batatas, Phytolacca dccandra, Saururus ccnniiis and Vag- 

 7icra stcllata. 



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. 



