crosier, crozier: the curled top of a young fern frond, also commonly referred to as a fiddlehead When a fern frond emerges from its underground rhizome, its head is coiled. Its appearance has been likened to a crosier (a bishop's curved staff) or the scroll on the head of some stringed instruments, hence the commonly used term fiddlehead.
frond: the leaf of a fern
Although people may refer to the leaves of palms and palm-like woody plants (cycads) as fronds, some botanists restrict the term to ferns. Each crosier (fiddlehead) that emerges from a fern's underground rhizome, is a coiled leaf or frond.
sporangium: a sac or receptacle in which reproductive spores are produced and stored Although sporangia...are often associated with fungi and seedless plants, such as bryophytes (e.g., mosses) and ferns, they occur in all plants sometime during their life cycles.