26 



PLANT RELATIONS. 



Fig. 20. A spray of maple, showing the adjustment of the leaves in size and position 

 of blades and length of petioles to secure exposure to light on a horizontal stem.— 

 After Kerner. 



etc., as to give ample evidence of the effort put forth by 

 plants to secure a favorable light-relation for their foliage 



Fig. 21. Two plants showing adjustment ot leaves on a horizontal stem. The plant 

 to the left is nightshade, in which small blades are fitted into spaces left by the 

 large ones. The plant to the right is Selaginella, in which small leaves are dis- 

 tributed along the sides of the stem, and others are displayed along the upper sur- 

 face.— After Kerner. 



