Perennial fern ally 5 - 40 cm tall Leaves: tufted, spirally arranged at top of rootstock, pale to lustrous black toward base, bright green, flexible, grasslike, 5 - 40 cm long, linear, slightly swollen near base, tapering to tips. The leaves shrivel, turn yellow and disappear after the spores have matured. Rootstock: underground, bulb-like, two-lobed, brown, nearly round, corky, with roots arising from central area between lobes.
Similar species: Isoetes melanopoda is quite similar to I. butleri, but that species only occurs in calcareous habitats such as dolomite prairies, and the large spores (megaspores) are usually more than 450 microns in diameter, further the megaspores are bumpy, and the microspores are light brown and warty.
Habitat and ecology: Very rare, possibly extirpated (extinct), preferring wet meadows and shallow ponds.
Occurence in the Chicago region: native
Notes: The Chicago Region is at the far northeast edge of the range of this species. Since it is often submersed in shallow water, it can be easily overlooked.
Etymology: Isoetes is from the Greek isos, meaning ever and etas, meanining green, referring to the evergreen character of the plant. Melanopoda means "black-footed", referring to the blackish base of the plant.
Lvs 7-40 cm נ0.3-1.2 mm, erect, not or scarcely twisted, with abundant stomates and usually 4 peripheral strands, usually blackish at base, and with a pale line down the middle of the adaxial side; sporangia (5-)8-15(-20) mm, finely brown-dotted at maturity; one-fifth to two-thirds covered by the velum; megaspores 0.25-0.45 mm wide, with tubercles or short low ridges; 2n=22. Amphibious, mostly in shallow temporary ponds, or nearly terrestrial; Minn. and S.D. to e. Tex. and Ala., e. occasionally to Ill., Tenn., nw. Ga., and reputedly s. N.J.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.