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 chlorophyl 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 canuabiniuti 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- 



