Isolated from the rhizomes of male fern: Boehm, Ann. 318, 253 (1901); 329, 310 (1903). Structure and synthesis: McGookin et al., J. Chem. Soc. 1953, 1828; Riedl, Ann. 585, 32 (1954); Aebi, Helv. Chim. Acta 39, 153 (1956). Crystal structure of α- and β-forms: Ermets, Penttil, Acta Chem. Scand. 24, 3335 (1970). Toxicity study: Airaksinen et al., Acta Pharmacol. Toxicol. 25, 33 (1967).