Found this growing out of a dry streambed near the Middle Fork Snoqualmie River. Plant is only ~ 6 inches tall.
Probably as with the young sword fern on the previous thread this one is not completely developed yet, showing its mature appearance.
I think Ron may be right. The leaves look similar to Botrychium michiganense but it has not been documented in Western WA. The only Botrychium on our plant list for King County is B. montanum which does not remotely resemble this plant. According to the NRCS plants database, Asplenium ruta-muraria only occurs east of the Mississippi. This is a remote site out in the forests of the Western Cascades. Not a place where you would expect to see rare garden escapees. Maybe some kind of stunted or disfigured Lady Fern? Strange that I did not see anything like this anywhere else in the creek, and I looked for about two hours.
Here is another photo of a similar-sized plant that was growing nearby. This one looks like Athyrium filix-femina.
According to the Plants Profile for Botrychium multifidum (leathery grapefern) Botrychium multifidum is present in the King County, Western WA. I don't know what was your exact location, it could be very near to the border of Kittitas County (where B. multifidum is not listed), but even if it was not inside the King County, there is a pretty good chance that the map is not extremely accurate or the plant has expanded its area recently. I think, that your initial photos are very similar to the leaf photo of Pteridophytes of Wisconsin: Botrychium multifidum, leather-leaved grape fern or File:Botrychium multifidum 4-eheep (5097437027).jpg - Wikimedia Commons, only plants on your photos are a bit too young and leaves are not fully opened yet.
I think you're right. I see now that this species is listed on my plant list as Sceptridium multifidum which was throwing me off. Looking at it more closely there does appear to be another pair of shoots in the 2nd photo branching off the main stem. Very cool... thanks!
