I can't get a close enough image to examine the spots thoroughly, but because they're evenly spaced, its most likely these are sporangia, or spore cases. It's a sign of a healthy plant and the spores are produced as part of the reproductive process.

Rust infection can be a problem on these plants in some areas, but the orange spots are randomly spaced, so if the plant seems otherwise very healthy, they're spore cases.

I can't get a close enough image to examine the spots thoroughly, but because they're evenly spaced, its most likely these are sporangia, or spore cases. It's a sign of a healthy plant and the spores are produced as part of the reproductive process.

Rust infection can be a problem on these plants in some areas, but the orange spots are randomly spaced, so if the plant seems otherwise very healthy, they're spore cases.

http://beyondthehumaneye.blogspot.co.uk/2009/11/polypody-fern-with-golden-sporangia.html