ADJUSTMENT TO SURROUNDINGS 139 



ing conditions of light, and clearly indicate that the chief 



FIG. 97. House geranium (Pelargonium), showing back and side views 

 of the same plant, grown with the same side always facing a window. (Cf 

 Fig. 98.) 



FIG. 98. House geranium (Pelargonium}. At the left, front view of 

 the same plant as shown in Fig. 97. At the right, about three days after 

 having been reversed, in front of the window. Note that only the upper, 

 younger leaves are properly adjusted to receive the light rays on their 

 upper surfaces; the lower, older leaves were not able to change the "fixed" 

 light position they previously assumed. 



function of leaves is to bring the plant into suitable rela- 

 tion to light. Its flat expanded form makes possible the 



