EXPLANATION OF THE PLATES. 



PLATES XXIII-XXV. SILVERY SPLEENWORT. Athyrium thelypteroides. 

 Plate XXIII. i. Young plant attached to prothallus. 2-6. Young leaves 

 in early stages of development. Plate XXIV. Young leaves in later stages of 

 development. Plate XXV. i. Mature sterile leaf. 2. Section of fertile 

 pinna of highly developed mature leaf, X 2\. 3 . Section of fertile pinna of 

 less highly developed mature leaf, X z\. 



