FLORA OF ICELAND elements: Athyrium distentifolia, Alpine Lady-fern, þúsundblaðarós

Athyrium distentifolia; The Alpine Lady-fern is a fern which can be found in mountain regions of the western, northern and eastern coastal regions. It grows on, in winter, snow covered slopes.
The bipinnate fronds are generally rather light-green. They are usually about 20cm - up to 50 cm long. The (second order) leaflets are finely and deeply dissected, the margins of the lobes more or less folded downwards.
The sporangia are round (more reniform/oblong in A. filix-femina). A characteristic of the indusium, the membrane that covers the spore-producing organs on the bottom side of the leaflets (to be more correct: the back side of the leaflets), is that it drops soon so is missing on mature plants. This is in agreement with their genus-name Athyia: from Greek "A" = without and "thyreos" = shield, referring to the lack or quickly dropping of the indusia in this genus. Note though that this is not the case in A. filix-femina.
It is member of the Athyriaceae, the Lady-fern family. The Icelandic name for this species is þúsundblaðarós.