Sori is a term used in botany to describe clusters of spore-producing structures found on the undersides of certain leaves, particularly in ferns. These structures contain spores, which are essential for the plant's reproduction. Sori can vary in shape, size, and arrangement, depending on the species of fern. In addition to ferns, sori can also be found in some fungi, where they serve a similar purpose in spore production. Understanding sori is important for studying plant reproduction and ecology, as they play a crucial role in the life cycle of ferns and fungi.