Seeds develop from structures called ovules, which are in the flowers or on the cones of a plant. Botanists divide seeds into two main groups, enclosed seeds and naked seeds.
Enclosed seeds are produced by angiosperms. Their ovules are enclosed by an ovary, a structure within the flower. As the seed ripens, the ovary enlarges and forms a fruit, which provides some protection for the developing seed. In some plants, the ovaries develop into fleshy fruits, such as apples and peaches. Other plants, such as peas and poppies, have dry fruits that form pods or capsules. In grain plants, such as corn and wheat, the ovary and ovule join together, forming a hard kernel.
Naked seeds are produced by gymnosperms. The most common type of gymnosperm are the conifers. Conifers produce ovules on the upper surface of the scales that form their cones. Gymnosperms have no ovaries, and so their seeds are not enclosed during development. However, the scales of conifer cones close up together when the seeds are ripening and provide some protection for the seeds.