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any of the spore-bearing vascular plants, including the ferns, club mosses, spike mosses, quillworts, horsetails, and whisk ferns. Once considered of the same evolutionary line, these plants were formerly placed in the single group Pteridophyta and were known as the ferns and fern allies. Although modern studies have shown that the plants are not in fact related, these terms are still used in discussion of the lower vascular plants.