"Iwa-yukinoshita" (Tanakaea radicicans) belongs to Saxifragaceae (the Saxifrage family). It is an evergreen perennial herb that is distributed to Kanagawa, Shizuoka, and Yamanashi prefectures in Honshu, and Kochi prefecture in Shikoku, Japan. It grows along valleys and on damp rock walls, and is 10 to 20 cm tall. The rhizomes crawl horizontally and spread out with runners. The leaves are elliptic to ovate-elliptic with serrated edges and the underside is usually dark reddish purple. It is dioecious, and flowers in conical inflorescences from May to June. The sepals of male plants are white and conspicuous, while those of female plants are green and inconspicuous.