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 2J. 



