Non-seed plants are plants that do not require seeds to reproduce and grow into new plants. Instead of using seeds, non-seed plants use structures called spores to create new versions of themselves. Like seed plants, some non-seed plants are able to produce their own food through photosynthesis, the process by which plants convert the sun's energy into sugar. Meanwhile, others depend on organic materials for feeding.
Horsetails are one example of non-seed plants that reproduce via spores. These spores essentially are small replicas of adult horsetails and become gametophytes, which feature both male gametes and female gametes -- essentially sex structures. When rain falls and enough moisture is present, the male gametes -- basically sperm -- move toward their female counterparts to produce an embryonic horsetail that eventually becomes a mature version of this non-seed plant.
Ferns are non-seed plants that feature a cluster of leaves called a frond, with each frond containing small leaves called pinnae. Underneath the frond are blotches that contain spores, which are important parts of the fern production process. The coverings around these spores are known as sporangia. In moist environments, spores -- which act like seeds -- grow into gametophytes, small plants that are shaped like hearts. These gametophytes possess just half of an adult fern's genetic material, but when fertilization occurs in a moist environment, the gametophyte becomes a sporophyte, which develops into an adult fern. Ferns have true leaves, stems and roots.
Mosses are non-seed plants that reproduce by first producing female structures called archegonia and male structures known as antheridia. These structures typically exist on different plants. The antheridia release sperm and fertilize the archegonia's egg cells to produce a zygote. The zygote eventually becomes a spore plant. The dividing of cells allows this spore plant to develop atop an archegonium. In addition, mosses can reproduce asexually. If moss leaves are cut from the plant, they can grow into independent plants. Mosses do not have true roots.
Liverworts produce new plants in a way similar to that of mosses. Instead of using seeds, they use archegonia and antheridia to achieve fertilization. Raindrops must be present for the antheridia's sperm to be able to reach the archegonia's eggs. In addition, leaves that fall from the plant easily can regenerate into new plants.