What is "lion's leaf"

Lion's leaf \Li"on's leaf`\ (l[imac]"[u^]nz l[=e]f`) n. (Bot.) A South European plant of the genus Leontice ( Leontice leontopetalum), the tuberous roots of which contain so much alkali that they are sometimes used as a substitute for soap.

n. ''(l mul Leontice leontopetalum)'', a South European plant, whose tuberous roots contain so much alkali that they were sometimes used as a substitute for soap.