The genus Achlys is one of the very reduced types of Berberidaceae. It contains two distinct species, A. triphylla (SM.) DC. and A. japonica MAXIM., the former being distributed on the Western coast of North America, the latter in Northern Japan and Northern Corea. The flowers are arranged in a spike, which has been derived from a compound pleiochasial cyme and possesses a terminal flower. The individual flower consists of nine stamens arranged in three cycles and of a single carpel with a basal anatropous ovule. There is no trace of perianth. The fruit is an achene. The genus is most closely related to Leontice and Epimedium.