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There are three well-marked classes of the Pteridophytes: the ferns (Filicin?); horse-tails (Equisetin?); and the club mosses (Lycopodin?).
Class I.-Ferns (Filicin?).
The ferns constitute by far the greater number of pteridophytes, and their general structure corresponds with that of the maiden-hair fern described. There are three orders, of