Sorus

A sorus is a cluster of sporangia, the structures that produce spores, on a fern or another spore-producing plant. In ferns, sori commonly appear on the undersides of fronds.

Sporangium: A capsule-like structure in which spores are produced and released. Each sorus consists of one or more sporangia.
Sporangium development: The growth and maturation of a sporangium, including formation of its spore-producing tissue. Sori form as their component sporangia develop on the frond.
Fern identification: The recognition of fern species using traits such as frond shape, scales, and reproductive structures. Sorus position, shape, and covering are useful characters for distinguishing fern species.
Strobilus: A compact cone-like reproductive structure made of spore-bearing leaves or scales. Unlike a sorus, a strobilus organizes reproductive structures into a cone-like axis.
Spore: A reproductive cell that can develop into a new organism without fusing with another cell. Sporangia in a sorus produce the spores that continue the plant's life cycle.
Fern spore dispersal: The release and transport of fern spores away from the parent plant. Mature sporangia in a sorus open to release spores into the air.
Fern anatomy: The study of the structures and organization of ferns, from rhizomes to fronds and reproductive organs. Sori are recognizable reproductive structures within fern anatomy.
Sporocarp: A specialized structure that contains or encloses sporangia, especially in certain aquatic ferns. Some ferns package sporangia in a sporocarp rather than exposing them as typical sori.
Fern frond: The divided leaf of a fern, bearing photosynthetic tissue and sometimes reproductive structures. Fern sori commonly form on the underside of a frond.
Leptosporangiate fern: A fern whose sporangia develop from a single initial cell and usually have a stalk and annulus. Most familiar fern sori consist of leptosporangia.

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