FORMATIVE INFLUENCE OF LIGHT 143 



nished, changes in function as well as many other alterations af- 

 fecting the general physiology and organography of the plant 

 ensue. 1 



217. Production of Primordial Leaf-forms by Diffuse Light. 

 Campanula rotundifolia forms two kinds of leaves, one rounded, 

 and cordate at base, on the lower part of the stem in the earlier stages 



Fig. 76. Cassia (a tropical species) showing normal position of leaves in mod- 

 erate illumination. 



of its development, and the other lanceolate or linear, in the later 

 stages. The first are developed from the stem when it is usually 

 more or less excluded from the light by the loose substratum, 

 while the latter are developed in the full illumination of sunlight. 

 To demonstrate this action establish a dozen healthy plants in 

 suitable pots in the spring and place them in a row, beginning 

 near a window and extending into a part of the room in which only 



•For full discussion of this subject see Goebel, K., Organography of Plants, 227. 

 1900. 



