lion's leaf

Wiktionary

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

GNU Webster's 1913

1. 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.