"Miyama-shishigashira" (Blechnum castaneum) belongs to the Blechnaceae family. It is an evergreen fern that is distributed from Hokkaido, Tohoku district to northern Kanto district and Hokuriku district of Honshu. The fern grows in the deciduous broad-leaved forest zone in the mountains and is 20 to 30 cm high. The leaves are remarkably dimorphic between fertile fronds and sterile fronds, and fertile fronds are about twice as long as sterile fronds. The petiole and the back of the leaf axis are dark purple-brown, with dense fine dots, and the texture is rough. The petiole is densely populated with linear scales.