david1945wagner's Identifications

Ultramafic outcrop near treeline
31726 VT, WTU
near plants of Polystichum lonchitis, P. lemmonii, P. kruckebergii
David Barrington (VT) writes 8 Jan 2024:
So, to get the crux of the matter your numbers 31726 and 31733 are confirmed as hybrids given on my study of the spores... 31726 also has irregular spores, but not many. So many of the sporangia remain unopened, though fully mature, and largely without contents except for what I Take to be a negligible amount of orphaned perispore clinging to the inside wall of the sporangium
These two do fall between the collections you sent of Polystichum lonchitis and P. kruckebergii morphologically. The character I found most useful was the ratio of the length to the maximum width for the medial pinnae—roughly 1:1 in P. lemmonii, 3:1 in P. lonchitis, and (though more variable) around 2:1 in P. kruckebergii. The two hybrids come in around 3:2.

This one stood out from a distance, with overall form strongly like P. lonchitis, but with noticeable toothed leaflets.

Very glossy and stiff leaflets, proportionally quite long.

The pressed specimen however strikes me quite differently. The glossiness is gone now, and without the tilt to the leaflets they look much more crowded and not as long & thin.

Not sure about the spores, but they look to have matured normally?

My original thought had been a hybrid of P. lonchitis x kruckebergii, but I'm less sure now.

If it isn't a hybrid, I would have called it P. lonchitis based on the general appearance in the field (perhaps this species can have occasional toothiness like munitum?), but based on the pressed specimen I would go with P. kruckebergii instead based on the crowdedness and rather deep divisions.

Growing on rock outcrop with several large clumps of P. kruckebergii (and lemmonii not far away), but lonchitis was also common throughout the area with scattered plants widely distributed.

Edit...
Repeat visit in 2023: https://www.inaturalist.org/observations/183925296
And Peter Zika's record: https://www.inaturalist.org/observations/182937780