Butler's quillwort

Plants terrestrial. Rootstock nearly globose, 2-lobed. Leaves deciduous, dull green to gray-green or yellow green, pale toward base, spirally arranged, to 15(--30) cm, pliant, tapering gradually to tip. Velum covering less than 1/4 of sporangium. Sporangium wall ± brown-streaked. Megaspores white, (360--)480--650 μm diam., obscurely tuberculate; girdle obscure. Microspores light brown in mass, 27--37 μm, papillose. 2n = 22.

Spores mature in late spring. Calcareous soil; limestone cedar glades, barrens; Ala., Ark., Ga., Ill., Kans., Ky., Mo., Okla., Tenn., Tex.

Population of Isoëtes butleri is locally abundant in open areas on alkaline soils saturated by water from early spring rains. The leaves yellow, wither, and disappear by late spring.