A-small brown specks on the underside of fronds (1) are known as sori (2) and are composed of numerous spore bearing bodies known as sporangia (3).

Ferns are not, of course, flowering plants. They reproduce by means of spores which produce an intermediate stage from which the fern plant develops.

B-From the spores develops a thin, green heart-shaped plant upon the underside of which are found organs whose general function is that of the stamens and pistil of flowering plants. The fern plant that we see develops from this intermediate stage.

C-The ferns along the trails serve merely to bear spores which in turn develop into the intermediate plant (prothallus) and these arise the spore bearing fern again to complete the cycle.