Aerial Parts of a Fern
Fern Rhizomes (Stems)
Arrangement of Sori on Fronds of Common Species
The rhizome is the fern's stem. Both roots and fronds are produced from the rhizome. They differ in size and shape in different species. They range in size from a tiny, insignificant plate to the tall trunks of tree ferns. Many are capable of creeping or climbing.
The sori (sing. "sorus") are the spore producing bodies that appear on the fertile fronds. They can be many different shapes and positions on the frond. some fern types have specialist fronds with a different shape from the everyday green fronds and are dedicated to the sori and spore production. The shape and arrangement of the sori is one of the features used to distinguish different fern families.
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The spores themselves are very small, almost microscopic and are produced in the 100's of thousands by the sori. If you place a frond with sori on nwspaper, sori side down and leave it in a warm dry place for a day or 2, when you lift the frond, there will be a pattern of shed spores in the shape of the sori.
