I20 



MEMOIRS OF THE NEW YORK BOTANICAI. GARDEN. 



Ipomoea Batatas Poir. 



Tubercles of the sweet potato placed in moist soil in the dark 

 room in November began to produce stems in January, and sent out a 

 succession of these organs, which were apogeotropic, but soon became 

 decumbent with the terminal portions curved upward. The apical 

 buds soon perished, and the lateral growing points began activity. 



The leaves developed petioles a half or two thirds of the normal 

 length, with the laminae folded with the ventral surfaces together. 

 The laminae did not attain a superficial area of more than a tenth of 

 the normal. The leaves were crowded together on the basal portion 

 of the stem, being not more than i or 2 cm. apart on a section 

 about 20 cm. long, in normal plants. Above this the leaves are 

 more scattered on a portion of the stem in which twining usually 

 takes place. This terminal twining portion was not developed in the 



etiolated plants. (See Fig. 75.) 



No important differ- 

 ences could be detected 

 between the structure 

 of normal and etiolated 

 stems. The leaves 

 quickly perished and 

 dropped off, leaving a 

 distinct protuberance at 

 the point of connection 

 with the stem. (Fig. 



75-) 



The tubercles per- 

 ished after the first eti- 

 olated growth, and the 

 plant does ^ not seem 

 adapted to making a 

 second effort in dark- 

 ness. 



Iris sp. 

 Shortly after root- 

 stocks were placed in 

 the dark room the buds 

 , , . , .^ . began activity, and a 



Fig. 76. Etiolated specimen of /r^.s and epidermis o 



of etiolated leaf. succession of leaves was 



