MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 37 



was not done until the completion of the experiment. Control speci- 

 mens were cultivated in the physiological laboratory on the same 

 floor of the building, or in the experiment chamber of the propagating 

 houses. 



The illustrations are mainly drawings from photographic prints, 

 from natural objects and from microscopic sections, and were made 

 by Miss Alexandrina Taylor, and Mr. Auguste Mariolle. 



The details of the observations on the several species of plants 

 brought under examination are given on the following pages. 



Agave Americana L. 



Specimens with thick fleshy leaves 25 to 40 cm. in length were 

 placed in the dark chamber in September, 1900, and the observa- 

 tions were closed in May, 1901. Leaves which had not reached 

 maturity at the beginning of the test elongated by basipetal growth, 

 forming a pale yellow etiolated basal portion. The chlorophyl in 

 the older green portion was maintained in an apparently normal 

 green condition during the entire eight months. Leaves emerging 

 after the beginning of confinement attained only half the length and 

 thickness of the normal, and were capable of extended existence in 

 the dark room. This endurance is coupled with the fact that the 

 stomata were present in the etiolated epidermis, open and apparently 

 normal in form with the guard cells richl}^ loaded with starch.'^'' 



The leaves were not so rigid as the normal. The teeth along the 

 margins were present, but were not so prominent as in the green 

 specimens. The outer walls were slightly cutinized, less so than 

 the normal, and did not show the usual thickening. The develop- 

 ment of the fibrovascular bundles was apparently arrested in an 

 early stage of the differentiation of the phloem and xylem. Spiral 

 vessels were fully formed, however, and could be pulled out in the 

 usual manner. 



No indications of flower spikes were to be seen in the etiolated 

 plants, or in the control tests. 



Allium Neapolitanum Cyr. 



Bulbs of Allium Neapolitanum were placed in the dark chamber 

 in March, 1901 and soon began to send out leaves. The bases of the 



■"Thomas, J. Anatomic comparee et experimentale des feuilles souterrainnes. 

 Rev. Gen. d. Bot. 12: 394. | 1900. 



