Asplenium platyneuron (Ebony Spleenwort)
|Also known as:|
|Habitat:||part shade, sun; mixed hardwood forest, woods, thickets, river bluffs, rocky slopes, mossy banks|
|Plant height:||4 to 20 inches|
|Wetland Indicator Status:||GP: FACU MW: FACU NCNE: FACU|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Leaves and stems:
Leaves are evergreen, 4 to 20 inches long, up to 3 inches wide, generally linear in outline but typically broadest above the middle and tapering at both ends, once-compound with 15+ alternate pairs of leaflets. Fertile fronds are taller and more erect than sterile fronds, which are often prostrate, and typically have more leaflets than sterile fronds. The leaflets are narrowly triangular, ½ to 1½ inches long with tiny rounded teeth. At the base of a leaflet is 1 or a pair of lobes (“ears”) which partly cover the stem. Veins are forked. The stem is dark reddish brown and glossy with small, dark brown to black scales at base. It forms asymmetrical clumps from a short rhizome.
The sori (group of spores) are produced in summer and are found on the underside of the leaf. The sori are linear with up to 12 pairs alternately arranged along the mid-vein. There is a translucent tissue (indusium) that partly covers the sori and is attached on one-side of the sori, but quickly shrivels and become inconspicuous. The spores are are dark-brown at maturity.
Ebony Spleenwort could be confused with Christmas fern (Polystichum acrostichoides) but the stem of Christmas fern is green and scaly, and its spores cover the back of a leaflet. In contrast, A. platyneuron has a shiny, dark reddish brown stem and the sori are linear, alternately arranged along the mid-vein. A Minnesota Special Concern species since 1996, according to the DNR, as of 2009 it had only been recorded a total of 12 times in 4 counties: Fillmore, Houston, Wabasha and Winona. A small population has since been discovered along a hiking trail in southern Hennepin County. While it is possible it was deposited there by foot traffic, unintentionally transported from another known location, it is still an addition to this rare species' total population in the state and gives us a little hope that more of it is out there, waiting to be found.
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Photos by K. Chayka, Peter M. Dziuk, and Cindy Hoffmann taken at Richard T. Anderson Conservation Area, Hennepin County.
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