MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 



187 



normal. The petiole at the base of the lamina was curved in such 

 manner that the lamina was held pendant in an inverted position in 

 the earlier stages of growth. With the growth of the petiole, this curve 

 became accentuated until finally the tip of the lamina was projected 

 upward, the petiole having curved through 360°. The epidermal cells 

 of the etiolated petioles measured about 280 by 9, and of the normal 

 about 65 by 9. The stomata were open and 

 functionally normal. The thickness of etio- 

 lated and normal petioles was about the same. 

 The laminae were rolled with the edges over- 

 lapping. Some of the stomata are functional 

 but the greater number are not differentiated. 



Viola rostrata Pursh. 

 Specimens of Viola rostrata were placed 

 in the dark chamber in January, 1900. The 

 shoot reached an extreme length of 18 cm. 

 and the petioles of 6 to 10 cm. The laminae 

 were not unrolled and were held pendant by 

 a curvature of the petiole at the base of the 

 lamina. In transverse section the epidermal 

 cells were seen to be muriform and the mid- 

 dle of the laminae consists of four or five un- 

 differentiated parenchyma cells with some air- 

 spaces. The stomata did not open. The 

 cross section of the petiole showed eight to 

 ten fibrovascular bundles with annular, spiral 

 and scalariform ducts present. The cortex 

 was composed of twenty layers of large cells, 

 equal to about half of the diameter of the pith. 

 Small intercellular spaces were to be seen in 

 the cortex. A subepidermal layer was slightly 

 thickened. The epidermal cells were slightly 

 papillose in places. No distinct cambium 

 ring was formed. The stipules of etiolated 

 specimens were about 4 by 7 mm., while in the normal they are but 

 3 by 1.5, thus showing an increase in size in darkness. 



The normal stem had a cortex about equal to the pith in thick- 

 ness and a heavy pericycle. A cambium layer was present in the 



Fig. 147. Viola ros- 

 trata, etiolated shoot. 



