EXPLANATION OF THE PLATES. 
Pirates XXVIII-XXX.—Massacuusetts FERN. Dryopteris simulata. 
Plate XXVIII.—1, 3-7. Young leaves in different stages of development. 2. 
Very young plant. Plate XXIX.—8. Young leaf in later stage of development. 
Plate XXX.—1. Mature sterile leaf. 2. Section of fertile pinna of mature 
leaf, X 24. 
