EXPLANATION OF THE PLATES. 
Pirates XXIII-XXV.—SILVERY SPLEENWORT. Athyrium thelypteroides. 
Plate XXIII.—1. 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.—1. Mature sterile leaf. 2. Section of fertile 
pinna of highly developed mature leaf, X 24. 3. Section of fertile pinna of 
less highly developed mature leaf, X 24. 
