Perennial herb with a rosette of long, terete leaves arising from a lobed,
cormlike base; roots numerous and branched, arising from the groove between
lobes of the corm. Leaves long, slender and terete, 10-50 cm long, 0.5-3.5
mm wide, mostly hollow with 4 longitudinal air chambers surrounding the central
vascular bundle, broadened at the base where the sporangia are contained; the
outer leaves producing megasporangia, the inner leaves microsporangia; sporangia
oblong, 5-30 mm long, usually brown-spotted, the megasporangia containing many
rather large (0.25-0.45 mm in diameter) megaspores, the microsporangia containing
numerous, tiny microspores. Jun--Aug. Submerged or in wet soil of swales and
temporary ponds; rare, with one old record from Mellette Co., SD, otherwise
scattered from MN to s NE; (NJ to MN and SD, s to GA and TX).
Isoetes melanopoda.The swollen bases of the quill-like leaves
contain the sporangia.