Aquatic-adapted plants, which bloom in water or are sometimes stranded on land, have been called var. stipulacea (although that epithet may not be the oldest one available for the taxon). They produce ovoid-conic to short-cylindric inflorescences 10-40(-60) mm, prostrate aerial stems, and leaf blades that are glabrous with acute to rounded apices. Terrestrial forms of this ecotype usually are spreading-pubescent and often bear ocreae that are foliaceous, green, and flared distally, characters found only in North American plants (R. S. Mitchell 1968).
Terrestrial-adapted plants, referred to var. emersa, bloom on moist soil and produce short- to elongate-cylindric inflorescences 40-110(-150) mm, spreading or erect aerial stems, and leaf blades that are appressed-pubescent with acute to acuminate apices. They produce ocreae that are entirely chartaceous and not flared distally. Emergent and terrestrial plants of this ecotype exhibit less phenotypic plasticity and a lower frequency of heterostyly than do plants of the aquatic ecotype (R. S. Mitchell 1968).
R. S. Mitchell and J. K. Dean (1978) and H. R. Hinds (2000) recognized var. amphibia, the Eurasian element, as introduced in New York and New Brunswick, respectively. These plants are morphologically intermediate between the North American ecotypes and often indistinguishable from North American plants (Mitchell and Dean).
The Meskwaki and Ojibwa used leaves, stems, and roots as a drug to treat a variety of maladies, the Potawatomi used roots to treat unspecified ailments, and the Lakota and Sioux used plants for food (D. E. Moerman 1998).
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