Ferns do not produce seeds, but instead bear SPORES on the underside of their FRONDS.
SPOROPHYLL are fern FRONDS that bear SPORANGIA, e.g. the ‘fertile fronds’ of ferns.
SPORANGIA are clusters of SPORES found on the underside of a SPOROPHYLL.
SPORES are the asexual reproductive cells on ferns.
Fern spores are contained in SPORANGIA, which are borne on the leaf surface in clusters called SORI.
SORI come in all shapes, sizes and locations.
Here on the Silver fern they appear as small brown dots.