Cyrtomium caryotideum has a number of common names: dwarf holly fern, dwarf netvein hollyfern, and fishtail holly fern, to name a few in English. Though fronds can reach approximately 70 cm, the “dwarf” part of the common names refers to how this species compares to others in its genus (Cyrtomium falcatum is about twice the height). Holly and fishtail are both allusions to how the pinnae resemble such things.
In today’s photograph, dozens of sori, or clusters of spore-producing structures, are obvious beneath each pinna. Fern spores when homosporous (all spores are roughly the same size and type), as they are in Cyrtomium, can permit long-distance dispersal. Light and very easily airborne, the spores of Cyrtomium caryotideum have likely helped this species disperse across a wide range: not only is the species native to Japan, but also China, Bhutan, India, Nepal, Sri Lanka, Taiwan, Philippines and Hawaii (link contains many photographs of the species).