Three hundred million years ago, ferns dominated the earth's surface, forming extensive marshes and forests with heights of over twenty-five meters. Today, fern

The definitive guide to Pennsylvania's plant life.

This systematic treatment of the ferns and allied plants provides a modern classification of the Pteridophyta based on an assess ment of the wealth of new data

The second edition of The Plants of Pennsylvania is the authoritative guide to identifying the nearly 3,400 species of flowering plants, ferns, and gymnosperms

Identifies over five hundred species.