266 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 



positions. Etioled leaves of Saiirurus developed onW short petioles^ 

 the clasping bases of which failed to keep pace with the thickening 

 of the stem and hence were soon cast off. The laminae remained 

 closely rolled and in a very primitive condition. The petioles were 

 held in a position variously appressed and the laminae were distorted 

 and the edges of the same were inrolled. Etiolated leaves of Viola 

 rostrata consisted of an excessively elongated petiole which assumed 

 an erect, or at times a horizontal position in older organs, and a lamina 

 which did not unfold and which was held in various positions by the 

 curvature of the petiole below the lamina. 



Only a comparatively small number of plants with perennial aerial 

 stems were cultivated in the dark room, and most of these have 

 already been discussed in various other groups, but it will be profit- 

 able to consider the action of the leaves with reference to the char- 

 acter of the stems from which the etiolated leaves arise. The species 

 included are as follows : Acer rubrum (p. i88), Baccharis halini- 

 ifolia (p. 80), Cornus alternifolia (p. 97), Fagiis Americana (pp. 

 105, 194), Populus Simonii {^. 154) and ^lercus (p. 166). 



Etiolated leaves of Acer consisted of a petiole much shorter than 

 the normal and a lamina which was fully extended with an outline 

 approximating the normal form, but much smaller in superficial area. 

 Functional stomata were present and the leaves had a duration of 

 about twent}' days. The suggestion arose during the course of the 

 experiments that the awakening of the leaves of this plant was stim- 

 ulated by illumination. The position of etiolated leaves was deter- 

 mined by their evident apogeotropism. Etiolated leaves of Baccharis 

 did not exhibit any tendency to an excessive elongation of the basal 

 portion, not attaining normal dimensions and were of brief duration. 

 Etiolated leaves of Cornus were much smaller than the normal, pre- 

 serving the ordinary relations of lamina and petiole, and were held 

 in various positions. Etiolated leaves of Pofulus offered similar 

 reactions, the proportions of the petiole and the lamina being about 

 the same as in the normal and both being much smaller than in 

 normal specimens. Here, as in Apios, the stipules were nearly 

 normal size and stature, being but little reduced. The leaves of 

 ^lercus assumed positions which in some instances were fairly 

 normal and the laminae were relatively more developed than the 

 petiole, the entire leaf being but a fraction of the size of the green 

 organ. The fibrovascular bundles were more clearly separated in 



