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Here is a closeup, showing the fern sori I discussed here: Because I just can’t get enough of gorgeous and unusual ferns, here are some more.

When you look at the back of a fern, you might think you are looking at a pile of spores Fern sori, a collection of microscopic but structurally complex sporangia.

Sporangia borne on elevated receptacles, forming roundish sori imperfectly covered by very delicate hood-shaped indusia attached to the base of the receptacles.

In some species of Puccinia the sori are so compact that they remain attached to the leaves long after they are dead and fallen.

But it is also frequently the case that the sori are produced on the upper side, distinctly within the margin, and where there are no corresponding sori beneath.