In this chapter we will take a close look at the manner in which the antheridium and archegonium give rise to gametes and at the act of sexual recombination. Formation of sex organs and the various physiological and genetic interactions between gametophytes represent one phase of the reproductive biology that terminates in sexual fusion and gene exchange. The final acts in this drama are gametogenesis and fertilization. In ferns, the function of gametogenesis is to construct two specialized reproductive cells, the spermatozoid (sperm), produced by the antheridium and the egg, produced by the archegonium. Fertilization involves the union of the sperm with the egg which is generally housed in a privileged location in the archegonium. In the first part of this chapter we will examine spermatogenesis, the origin of the sperm and follow it up with oogenesis, the formation of the egg and conclude our traverse of the gametophytic landscape with an account of fertilization.

Topics covered in this chapter have been reviewed by Duckett (1975), Bell and Duckett (1976), DeMaggio (1977), and Bell (1979b) and the reader is referred to these sources for additional information.

Spermatogenesis

Our knowledge of spermatogenesis in ferns is of recent vintage, derived largely from some careful work on Pteridium aquilinum, Marsilea vestita, and Ceratopteris thalictroides, which has provided a rich heritage of new information and some excellent electron micrographs.