Gymnocarpium dryopteris, Oak Fern

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Gymnocarpium dryopteris(Oak Fern)

Greek: gymnocarpium, naked fruit, referring to the lack of an indusium to cover the sporangia ; dryopteris, oak fern

A stand of Oak Fern, Gymnocarpium dryopteris, whose delicate ternate fronds seem to be in circular motion
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Sori of the Oak Fern, Gymnocarpium dryopteris, are produced on the back of the leaflets. Each sorus, composed of 50 or so sporangia, appears to the naked eye like a little brown dot on the back of the leaflet. Gymnocarpium sori lack an indusium.
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Oak Fern spores, Gymnocarpium dryopteris

Spores of the Oak Fern. These spores are about 40 microns long. Less than half the thickness of a hair.