LEAF-ARCHITECTURE AS ILLUMINATED BY A STUDY OF PTERIDOPHYTA. 693 



b c 



Fig. 25, a-e. —Juvenile leaves of Cyathca insignis, illustrating their progressive 

 development, (x 4.) 



Fig. 26, a-i. — A series of juvenile leaves, many of them actually cotyledons, of Pteridiwm aquilinurn. They illustrate 

 steps of progression from equal dichotomy to the scorpioid sympodium. The differences in size are largely due to 

 greater or less advance of the individual development, (x 5.) 



