Ferns, (Pteridophytes) belong to the higher cryptogams. The "crypto" or "hidden" refers to their being flowerless or having no obvious means of reproduction. So how DO ferns reproduce?

If you look at the underside of a mature fern frond you will often see small raised structures called sori.

As can be seen from the accompanying images, there is a huge variety of sori arrangement depending on the species of fern.

On closer examination, other structures become apparent. Often, a papery umbrella like structure called the indusium covers the sori. (Move the mouse over the picture for label)