(Dryopteris filix-mas), an herbaceous perennial plant of the family Aspidiaceae. The leaf blades are twice pinnate, and the petiole and the rhizome have large, dark scales. The sori have budlike indusia, which are distributed on the lateral veins of the leaf blade segments. The male fern grows in shaded areas under shrubs in the forest zone of Eurasia and North America. An extract from the rhizome is used as a vermifuge for tapeworms and pinworms. The rhizomes also contain substances (by-products of filicinic acid) that cause muscular paralysis of intestinal parasites.