Isoetes melanopoda (Prairie Quillwort)
|Also known as:||Black-foot Quillwort|
|Habitat:||part shade, sun; pools in rock outcrops|
|Fruiting season:||late spring to mid-summer|
|Plant height:||4 to 16 inches|
|Wetland Indicator Status:||GP: OBL MW: OBL NCNE: OBL|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Flowers are not produced, reproduction is by spores.
Leaves and stems:
Leaves are all basal, narrowly grass-like, erect to spreading, pliant, bright green, 4 to 16 inches long, about 1 mm wide, gradually tapering to a pointed tip, and arise from a fleshy, nearly round rootstock.
The leaf base is abruptly expanded and initially pale, usually turning shiny black on the outer surface with maturity. Plants are at least partly submerged in spring but later may become stranded on land or in the mud when pools dry up and water recedes.
Spores are produced starting in late spring, in an oblong-elliptic sac (sporangium) on the inner face of the leaf base. Translucent tissue (velum) covers at least a portion of the tip end but less than 75% of the sac. Two types of spores are produced: megaspores (female) are visible to the naked eye, white at maturity, .28 to .44 mm diameter with an obscurely wrinkled surface; microspores (male) are gray and 1/10th the size of megaspores.
Prairie Quillwort is a rare fern ally in Minnesota, where it reaches the northern edge of its range; the Minnesota populations are actually disjunct by more than 150 miles from the next closest population and several hundred miles from the main populations in Missouri and Arkansas. In most regions it is found in wet or seasonally wet places, such as meadows, ponds and ditches, but according to the DNR, in Minnesota it is restricted to rainwater and seepage pools in quartzite rock outcrops in the southwestern corner of the state. It was listed as Endangered in 1984 largely due to its specific microhabitat requirements here and limited number of populations.
Prairie Quillwort, also commonly known as Black-foot Quillwort, is one of three Isoetes species in Minnesota, the only one found in rock outcrop pools in the southwestern part of the state, and the only one where the leaf bases turn black at maturity, though there is an uncommon form (f. pallida) that stays pale at maturity. The other two species, Spiny-spore Quillwort (Isoetes echinospora) and Lake Quillwort (Isoetes lacustris) are found in fresh water lakes, ponds and streams in the northern half of the state. Each has a different texture to the megaspores; I. echinospora spores are up to .55 mm diameter with a spiny texture, I. lacustris spores are over .55 mm diameter with irregular ridges. A good hand lens or microscope is recommended.
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- Prairie Quillwort plant
- Prairie Quillwort rock outcrop habitat
- leaf bases are typically shiny black at maturity
- immature or f. pallida leaf bases are pale
Photos by Peter M. Dziuk taken in Rock County. Black leaf base photo by Larry Allain, U.S. Geological Survey.
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