Talcott Mountain State Park / Ridge Loop - Spores On Ferns
This closeup shows one fern frond with spores beside another without them. Some species have the sporangia (clusters of spore cases) on all fronds - this is not one of those, as you can see. The spores, more primitive than seeds, carry everything needed to produce new ferns.
Though primitive, spores are actually quite complex. Unlike seeds, which are fertilized prior to being distributed, spores carry a tiny clone of the fern which has the genetic material of both sexes. The material is only cross fertilized if and when the spore ends up in a suitable environment. The resulting growth replaces the original with a new plant that grows into a fern.