576 



MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 



eter less than the normal. These external alterations were accom- 

 panied by modifications of the structure of the tissues of the various 

 parts of the flower. Parenchymatous cells were larger and showed 

 a multiplication of their number in some instances. Both pollen 

 grains and ovules were smaller than in the normally grown flower. 



Fig. 170. Petunia. A, B and C grown under conditions in which daylight was 

 supplemented by electric illumination. Z>, E and jF, normal. After Bailey. 



It appears therefore that no autotropic chlorophyllose species 

 develops flowers unless the buds are subjected to the action of light 

 during some part of the period of development, or that some portion 



