The great variety of beans we eat are seeds. Many beans, such as pinto beans and kidney beans, have a hard outer covering called a seed coat that is the primary specialization of the seed to protect the embryo during dispersal. If you wanted to cook beans, then you would soak them overnight to soften the seed coat. We can also do this to make the seed coat easy to remove. Once the coat is removed, then we can see the embryo. The embryo is simply a small plant body, and it already has most of its basic parts.
Some of these embryonic body parts are also relatively specialized. For example, among the most prominent features of the seed plant embryo are its cotyledons. The cotyledons are sometimes called seed leaves, and we can think about them as the first leaves that are formed by the embryonic plant as it developments. The embryo can also have other leaves in addition to the cotyledons, but the cotyledons are the most prominent leaves that are present on the embryo. Among some plants the cotyledons are specialized for nutrient storage. In the life cycle of a plant, after the embryo has formed and the seed is developing, the parent plant moves nutrients into the seed. These nutrients will be critical for the further development of the embryo once the seed has separated from the parent plant. In some seed plants, such as bean plants, these nutrients that enter the seed are stored in enlarged cotyledons. Because of their function in nutrient storage in the seed phase of the life cycle, cotyledons do not look like the normal foliage leaves that we typically associate with plants.
If we remove one cotyledon from our bean embryo, we can see the other basic parts of the plant body that are already present. These include a root and stem, which bears additional young foliage leaves.
