24 



adaptajrion for more liglit. Other tilings also affect sticIi le&ves; 



Tlieoretically leaves should l)e more compoinid above but the reverse 



is usually true. 



Plants may "be oone- shaped as mullein with broad leaves, and 



the inverted cone with dissected leaves as Ambrosia. This is 



Kerner's view but it is not adjustable to facts. The shape of a 



leaf 



]^X^)^)^ does not determine the shape of k plant, but the surrounding's 



generally decide mt. The elm becomes cone-shaped when grown in 



the forest, but in the open is the reverse. 



Kerner's theory of light does not explain leaves wholly. 

 As to form the leaf is somewhat influenced by light but more so by 

 other factors. As to size, horixontall^r and vertically, light 

 has very little to do with it. As to position and arrangement, 

 Kerner's view is much more important. 



AdfligslQA SiL CO?,. 

 What is influence of COjl on leatff shape and arrangement ? COj^ is 

 necessary in large qixantities. Conditions favorable to admission 

 of light are alos favorable to admission of CQx ', biit light onl:^ 

 enters from one side while 00^^ comes in from all sides. 



Warming thiiiks that since CO4 is so plentiful there is no 

 necessity for special modifications to admit it. From recent 

 experiments it has been proved that CO^ is more plentiful in lower 

 leaves hence 00^ may influence the shape. 



Admission jil il. 

 TTo question as to quantity except in water-plants especially in 



