1911 Encyclopædia Britannica/Moonwort

MOONWORT, or Moon-fern, in botany, the popular name of a small fern (Botrychium Lunaria), belonging to the order Ophioglossaceae (see Ferns). It has a tuberous root-stock and a stout fleshy glabrous frond 3 to 6 in. long, with a sterile and fertile portion; the former bears several pairs of close-set, semi-circular or moon-shaped pinnae, the latter is pinnately branched and covered, on the face opposed to the sterile portion, with small globose spore-cases which burst transversely. It is a widely distributed plant in the north and south temperate and cold zones, and is found in pastures and grassy banks in Britain.

From Strasburger’s Lehrbuch der Botanik, by permission of Gustav Fischer.
Botrychium Lunaria.