Kerria Says Nothing but Longs: A Study of the Related Textual Research on Changdi and Tangdi

I first encountered kerria (Kerria japonica) on my third time joining the phenological observations of the Peking University Green Association. "So this is what kerria looks like! It is the plant used in the Book of Songs to symbolize brothers, isn't it?" Later I realized my memory was mistaken! What the Book of Songs refers to is "changdi," while "changdi" and "kerria" are two completely different plants. In addition, there are also "tangdi" and "tangdi" (written with different characters), and the four sound similar and look alike, and are often confused.