Flowering plants have evolved from plants without flowers. It is known that the function of several genes, called MADS-box genes, creates shapes peculiar to flowers such as stamens, pistils and petals. Plants that do not produce flowers, such as mosses, ferns and green algae, are also known to have the MADS-box genes. However, it was not well understood how the MADS-box genes work in plants without flowers until now. In order to understand the mechanism of flower evolution, it is necessary to understand how the MADS-box genes work in plants without flowers.