Characteristics
The ferns are an extremely diverse group, and there is no single characteristic that defines them. The following features are present in most:
Leaves, called fronds, are megaphylls. Most are compound with a rachis and numerous pinnae (or compound once again with pinnules). Almost all have circinate vernation—they are coiled (circinate) tightly in “shepherd's crook” or crozier fashion over the growing tips. These unroll as they mature (growth from the base to the tip like this is termed acropetal). The croziers are called fiddleheads and are eaten by some people, although many species are toxic.