Excerpts from Jim Conrad's
Naturalist Newsletter

Lady Fern, ATHYRIUM FILIX-FEMINA

from the August 16, 2009 Newsletter, reporting on a visit to Rogue River National Forest in southwestern  Oregon:
LADY FERNS

Relative to the Southeast, ferns in this area are more abundant but much less diverse. In my teeny home county, McLean, in western Kentucky, I found 16 fern species. So far around here only five species have turned up. Of these, one was Bracken, the world's most common fern, and two were super-abundant, look-alike swordfern species.

Therefore, during my hike along the Rogue, when the trail dipped into a moist, shady little valley and a different fern species suddenly showed up, lots of knee-high, frilly ones, I was tickled. You can see one above.

I knew this one from back in Kentucky. It's the Lady Fern, ATHYRIUM FILIX-FEMINA, one of the most common and best known ferns species throughout the temperate zones of both North America and Eurasia -- it's "circumboreal." Among its field marks are the way its lower divisions, or pinnae, are much smaller than at the frond's middle. Also, look at the frond underside below:

sori of Lady Fern, ATHYRIUM FILIX-FEMINA

In that picture, one feature confirming that it's a Lady Fern is that the veins DON'T reach the pinna's margin. Another feature is the special shape of each cluster of tiny, black spheres. Each of those clusters is a fruit-dot or sorus. The tiny, black spheres making up the sori are stalked, baglike sporangia. When a sporangium matures it bursts and releases spores, which under perfect conditions germinate to form tiny, flat things called prothalli (singular prothallus), the first stage of a fern's life cycle.

Anyway, the sori are said to be kidney-shaped, or "reniform." Earlier they'd been covered with cellophane-like indusia, and each indusium had been attached by one side, not in the center, umbrellalike, as with the swordferns. You might enjoy comparing the Lady Fern's sori with those of our abundant swordferns at http://www.backyardnature.net/n/09/090503sg.jpg.