Walking through the woods, you come upon a patch of ferns. You notice small, scabby-looking brown dots on the underside of the fronds. What are they, and what is their function?

Question

Walking through the woods, you come upon a patch of ferns.  You notice small, scabby-looking brown dots on the underside of the fronds.  What are they, and what is their function?

kittiwitti1 · Answer

Those are fern spores.
A spore is a unit of asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavorable conditions.