A sorus (pl. sori) is a cluster of

sporangia A sporangium (; from Late Latin, ) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, and many other lineages form sporangia at some point in their life cy ...

(structures producing and containing spores) in

fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes exce ...

s and

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately fr ...

. A coenosorus (plural coenosori) is a compound sorus composed of multiple, fused sori.

Etymology

This New Latin word is from

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic pe ...

σωρός (''sōrós'' 'stack, pile, heap').

Structure

In lichens and other fungi, the sorus is surrounded by an external layer. In some red algae, it may take the form of depression into the thallus. In ferns, the sori form a yellowish or brownish mass on the edge or underside of a fertile frond. In some species, they are protected during development by a scale or film of tissue called the indusium, which forms an umbrella-like cover.

Lifecycle significance

Sori occur on the sporophyte generation, the sporangia within producing haploid meio spores. As the sporangia mature, the indusium shrivels so that spore release is unimpeded. The sporangia then burst and release the spores.

As an aid to identification

The shape, arrangement, and location of the sori are often valuable clues in the identification of fern taxa. Sori may be circular or linear. They may be arranged in rows, either parallel or oblique to the costa, or randomly. Their location may be marginal or set away from the margin on the frond lamina. The presence or absence of indusium is also used to identify fern taxa.

Gallery

Image:Сорус папоротника Polypodium aureum.jpg, Sorus of '' Phlebodium aureum'' Image:Scattered-sori.jpg, Scattered sori Image:Linear sori.jpg, Linear sori Image:Dense sori.jpg, Sori covering a frond's entire underside ( acrostichoid) Image:Immature sorus.jpg, Fern sorus with immature sporangia Image:Round sori.jpg, Circular sori with mature sporangia Image:Rumohra adiantiformis sori 01.jpg, Sori with indusia at different stages of development. File:Triphragmium ulmariae, Meadowsweet Rust.jpg, Fungal sori of the Meadowsweet Rust gall. File:Large Sori (fern).JPG, Large sori File:Polypodium vulgare, sores (Matthieu Gauvain).JPG, ''Polypodium vulgare'' File:Sword fern sori, scale bar 1 mm.tif,

Sword fern Sword fern is a common name for several ferns and may refer to: *''Nephrolepis'', a tropical genus of ferns, especially: **'' Nephrolepis exaltata'', commonly cultivated as a houseplant, including the Boston fern *''Polystichum'', a cosmopolitan ...

. The indusia have opened, revealing the sporangia. Scale bar, 1 mm

References and external links