Serum

For the Venezuelan locality, see Soro (Sucre). Soros on the underside of a fern. Across a fertile fringe of Dicksonia antarctica. Each nucleus is an individual serum.

In the ferns, a serum is a group of sporangia located on the edges or backs of a fertile frond in true ferns and on the surface of fungi and lichens.

In many species of ferns the serums are protected by a cover called an Indian. Sera are formed in the generation of sporophytes; the sporangia within produce haploid half-spores. As the sporangia mature, the indusio withers and the spores can not yet be released until the sporangium is destroyed and releases the spores.

The shape, arrangement and location of the serums are valuable points for the fern taxonomy. Sera can be circular or linear; in rows, parallel or oblique to the margin, or randomly. Also the presence or absence of the indusio is used for taxonomy. and

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