A First Report on Pseudomeiotic Sporogenesis, a Type of Spore Reproduction by Which "Sterile" Ferns Produce Gametophytes

Abstract

Among the ferns there are two classical types of life cycles involving spore reproduction-the normal sexual life cycle, first described by Hofmeister in 1864, and the obligate-apogamous life cycle, discovered by Farlow in 1874. These are now so well known that it is necessary to say only that in the sexual life cycle, a diploid sporophyte gives rise to haploid spores, which form haploid gametophytes. The latter produce haploid eggs and sperms, and upon fertilization, these yield new diploid sporophytes (Fig. 1A). In the obligate apogamous life cycle, details of which were established by D6pp in 1932 and later confirmed by Manton (1950), the sporophyte produces diploid spores which form diploid gametophytes. The gametophytes tend to form antheridia with viable sperm but few or no archegonia. Production of a new sporophyte is accomplished simply by proliferation of cells from the diploid gametophyte (Fig. 1B). Other methods of reproduction in ferns are known, such as the various types of vegetative offsets from sporophytes or gametophytes, but no spores are involved. Only two basic patterns of reproduction involving spores, briefly described above, are known to occur.