Publication: Amer. Naturalist. 8: 215. 1874.
selected vouchers: WTU
Notes: Isoetes opaca is an invalid name. From Kanchi Gandhi:
1) Braun provided the name, but did not validate the name; it was Engelmann who validated the name.
Amer. Naturalist. P. 215: https://www.biodiversitylibrary.org/page/41393225#page/226/mode/1up
2) “Isoëtes opaca Nuttall” (p. 389) is an invalid name (a pro synonym).
P. 389: https://www.biodiversitylibrary.org/item/28731#page/487/mode/1up