Isoetes melanopoda (Prairie Quillwort)

Plant Info
Also known as: Black-foot Quillwort
Genus:Isoetes
Family:Isoetaceae (Quillwort)
Life cycle:perennial
Origin:native
Status:
  • State Endangered
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):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower:

Flowers are not produced, reproduction is by spores.

Leaves and stems: Leaf attachment: basal Leaf type: simple

[photo of leaf clumps] 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.

[photo of plant base] 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: Fruit type: spores on leaf

[photo of spore sac] 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.

Notes:

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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More photos

Photos by Peter M. Dziuk taken in Rock County. Black leaf base photo by Larry Allain, U.S. Geological Survey.

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