SELBY: STUDIES IN ETIOLATION 73 
Here we have wider divergence amounting to more than 5 per 
cent. difference in the dry substance of the normal above that of 
the etiolated stems. 
Rootstocks of Euphorbia Cyparissias were brought from Wooster, 
Ohio, to the New York Botanical Garden, and after these had shown 
signs of activity were placed in suitable pots and some exposed to 
light while others were placed in the etiolating chamber, on March 
20, 1903. The new stems were one to two cm. in height although 
none had formed chlorophy]l to any noticeable extent. One month 
later the stem-lengths of the normal and etiolated plants were re- 
spectively 8 to 10 cm. for the normal and 6 to 8 cm. for the etio- 
lated. It is evident that this plant does not support the assump- 
tion that light exercises an actual retarding effect upon growth. ~ 
Roots of Apocynum cannabinum were lifted and potted in 
November, 1902, and at this time duplicate pots were placed in 
the dark chamber and in the propagating house of the Garden; a 
large number of duplicates were cared for in the propagating house. 
The plants showed little tendency to make early growth in either 
situation. Toward the end of April, 1903, shoots began to ap- 
pear on the plants in the dark chamber and a corresponding 
plant was set aside in the propagating house. In June, 1903, 
measurements were kindly taken by Dr. W. A. Cannon, labora- 
tory assistant at the New York Botanical Garden. The etiolated 
plants attained a height of about 30 cm., while the normal speci- 
mens made no marked growth after having been set aside in April. 
Similar results to those of Apocynum were obtained with roots 
of Asclepias syriaca. In this case the etiolated specimen attained 
a height of 30 cm. while the normal plant attained a length of but 
5 to 6 cm., development being arrested for some reason. 
Interpretation of results 
It is evident from the foregoing that the phenomena of etiola- 
tion are not in themselves to be regarded as of a useful adaptive 
Character, as put forward by many writers on the subject. In 
Some instances it is conceivable that the undue elongation of 
Stems that ensues might serve the useful purpose of carrying the 
apical part of the stem with its leaves past an obstruction inter- 
cepting the light, but a census of the species which have been sub- 
