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Gymnosperms are a large classification of seed plants whose seeds are not enclosed within a fruit. Gymnosperms were the most prevalent phylum during the Mesozoic epoch. They have evolved to live in bogs with nitrogen-deficient soil or in regions where freshwater is lacking for part of the year.

• Gymnosperms are classified into four different phyla. Seed development and secondary cambium production are comparable in Cycadophyta and Ginkgophyta (cells that generate the vascular system of the trunk or stem and are partially specialised for water transportation).
• Gnetophyta is the closest group to angiosperms since they produce genuine xylem tissue with vessels, as well as the tracheids present in the rest of the gymnosperms.