ショウブ
"Acorus americanus" was formerly classified as "Acorus calamus" var. "americanus". It differs only in being a fertile diploid (2n = 24)], whereas most of the "A. calamus" of Europe and Asia is a sterile triploid species, that only spreads asexually. Diploid plants in northern Asia may be representatives of "A. americanus". Also as a diploid it does not produce b-asarone.