36 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 



The earlier etiolations from 1895 to 1899 were made at the Uni- 

 versity of Minnesota in small portable chambers of zinc and wood, 

 and the cultures were examined for a few minutes every day in day- 

 light, a method which is found to offer results markedly different 

 from those kept in absolute darkness and examined by the light of a 

 single candle not oftener than once a day. 



For a portable chamber the best material was found to be zinc, and 

 this was built in the form of a small house with no bottom. The 

 entire chamber rested upon a bed of sand about 5 cm. in depth, 

 upon which the plants were placed. The chamber was lifted from its 

 position b}^ means of a cord attached to the top passing over a pulley 

 fastened to a beam above. When the chamber was lowered to its posi- 

 tion the edges were imbedded in sand in such a manner as to exclude 

 light absolutely. Ventilation was provided by means of tubular 

 openings to which sections of rubber tubing were attached. The 

 curvatures of the tubing prevented access of light. Such portable 

 chambers were protected from the direct action of the sun's rays, and 

 injurious temperatures were thus avoided. 



Upon my removal to the New York Botanical Garden in 1899 the 

 work was resumed in a specially constructed dark chamber. This 

 chamber measures 5x5x6 meters and is situated in the middle of the 

 laboratory suite on the fourth floor of the museum building, and is pro- 

 vided with ample connections with ventilating shafts in such manner 

 that the atmosphere is always normal. Cultures were made here 

 between October and Ma}- of each year, and during this period the 

 temperature was constant between 17 and 21° C, and did not traverse 

 this range in less than four days, so that for most purposes a constant 

 temperature was provided in these tests. It is to be understood of 

 course that this temperature is by no means suitable for all of the 

 forms upon which observations were made, a fact which was duly 

 noted in the descriptions of the separate experiments ; it did permit, 

 however, a fairly etiolated normal development of almost all of the 

 species examined. Entrance to the chamber was gained by a set of 

 double doors with a vestibule between in such manner that no day- 

 light was admitted. Examination of the plants was made by means 

 of the light afforded by a single candle, or an electric hand-lamp of 

 four candle-power. 



In a few instances the etiolated specimens were removed for 

 the purpose of making photographic negatives, but generally this 



