Dog asks Jing, also known as: swamp equisetum. Perennial herbs. Rhizomes creeping, slender, dark brown, usually with tubers. Stems are often clustered, with a height of 14.5 ~ 36 cm; Thin, with deep grooves, 5 ~ 12 ribs, often with whorled branches, sparse and solitary, with small holes in the center, branches bent obliquely upward and inward, and withered in autumn. Leaf sheath teeth triangular-ovate, brown at the top, white at the edge, membranous, extending to the top into long white bristles. Sporangium spike is oblong, pedunculate, terminal, first purple-brown, then yellow; Sporangium is born under the peltate spore leaves, and the spores are isomorphic. There are two filiform elastic filaments, which wrap around the spores in a cross shape and bounce off when exposed to water to reproduce. Wild in paddy fields, ditches and wet places.