Fern spores

Now is the season of sporulation.  This is how ferns produce spores which eventually give rise to new ferns.  Spores are much smaller than most seeds and float in the air.

Here is a Hart's Tongue Fern (Asplenium scolopendrium) with one of the fronds turned over to show the long, brown sori on the underside.

Male fern (Dryopteris filix-mas) has more divided fronds and the sori are round or 'kidney'-shaped.

 Lady fern (Athyrium filix-femina) is more delicate and frilly 

and the sori are half-moon or j-shaped.

Soft shield fern (Polystichum setiferum) is divided so that each little pinnule is like a mitten with a thumb.

Sori in this photo are pale and unripe.