EXPLANATION OF THE PLATES. 



PLATES XXXI, XXXII. MARGINAL SHIELD FERN. Dryopteris margin- 

 alls. Plate XXXI. i. Young plant attached to prothallus. 2-8. Young 

 leaves in different stages of development. Plate XXXII. i. Mature sterile 

 leaf. 2. Fertile pinnule of mature leaf, X 2$. 



