Sori

Several years ago my wife harvested some ferns near the camp, brought them home and transplanted them into one of her flower gardens. Ferns add a nice touch, but we had no idea that they would literally overtake everything.
I often wondered how ferns multiplied and recently found out while relaxing on our front porch one afternoon. I noticed that one of the ferns had hundreds of tiny rusty brown spots on the underside of each frond (leaf). At first I thought I was seeing the eggs of some sort of insect, but later found out that they were actually “sori”.
Sori hold the spores or seeds of the fern and will eventually fall to the ground where it will disperse these spores to allow the plant to propagate.