Mystery Solved! Unknown Fern Identified!

East-facing hillside off the back of our property

It's early January and finally getting cold here in Maryland.  Now that there is not a lot of green leafy cover, it's a good time to spot some small evergreen native plants.  Most of the recognizable of these now are evergreen ferns, such as Christmas fern (Polystichum acrostichoides) and ebony spleenwort (Asplenium platyneuron).

As I was taking a look around I found another clump of a small evergreen fern that I have been trying to ID for the past two years.  It's growing on a wooded hillside off the back of our property.  This time with the one I found had fertile fronds showing the spore-producing sori underneath.

Unknown fern as I found it in January 2015; with only sterile fronds present.

Pictured here is a similar plant a little further down the hill.  In addition to the closely paired sterile pinnae at the base, this one has much longer stems bearing fertile pinnea (leaflets).

Fertile fronds are longer, 8-10", growing out the the center of the clump. 

With the additional information on the shape and placement of these reproductive organs I could make some more guesses at its identity.  The sori are brownish and fuzzy and are surrounded by 5 or 6 appendages that give them sort of a star-like appearance.  The sori are scattered midway between the center and midrib of the pinnea.

Close examination of the undersides of these fertile fronds show the reproductive organs, the sori.

Using a fern guide (Peterson's) I keyed it out to be of the genus Woodsia...but which one?  Since it has few hairs on it I really got stuck on it being smooth woodsia (W. glabella).  But that fern is rare and its range is much further north  in northern New England and Canada.  

So, while it is not normally in my nature, I decided to ask for help and posted my photos to on-line group that helps with native plant ID.  I quickly got a suggestion to consider it as blunt lobed cliff fern, Woodsia obtusa.  This is a relatively common species in eastern US and its description lined up pretty well with my plant.  What was throwing me off was the drawing in the guide showing lots of hairs and glands on the rachis (central stem).  Looking at images of Woodsia obtusa on the internet from knowledgeable sites showed them to be consistent with the plant in our 'backyard'.

Fern ID is tough and it is good to have multiple resources to help with ID.  Also getting assistance from other plant enthusiasts can be an invaluable learning experience, and a great savings of time, too. Thanks to all of you out there!