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Homosporous vascular plants are typically depicted as extreme inbreeders, with bisexual gametophytes that produce strictly homozygous sporophytes. This view is promulgated in textbook life cycles despite ample evidence that natural populations of most species regularly outcross. We review research on a variety of mechanisms, including genetic load, asynchronous production of eggs and sperm, and pheromonal control of gamete production, that actively promote heterozygosity in ferns and lycophytes. Evolution of the land plants cannot be reconstructed without accurate depictions of the unique life cycle that has helped make ferns the second most diverse lineage of vascular plants on Earth. With revised illustrations and definitions, we provide scientists, educators, and students with a contemporary understanding of fern and lycophyte reproduction, revealing them as evolutionarily dynamic and exploiting a wide range of mating systems.

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Populations of a fern gametophyte presumed to be of the genus Vittaria occur commonly in the uplands of the southeastern United States. The gametophytes occur on non‐calcareous rock outcrops of various composition in areas which provide continuous moisture and protection from temperature extremes. Gametophytes in these habitats are robust and long lived, frequently forming the dominant vegetation in areas covering several square feet. Reproduction is exclusively vegetative by production of gemmae. Although sex organs are present in most populations, viable sporophytes are never produced. The gametophytes have previously been considered most likely to be V. lineata, which occurs in Florida, but morphological and physiological comparisons do not support that conclusion. Significant differences between Appalachian and Florida gametophytes occur in growth form, growth rate, cold hardiness, sporophyte production, and patterns of gemma production. The distribution of the Appalachian gametophytes correlates with old, unglaciated land masses suggesting antiquity rather than recent introduction. Present evidence favors the interpretation that the Appalachian Vittaria gametophytes either belong to a tropical American species from which they have long been separated, or that they represent a distinct species of which the sporophyte no longer exists.

Vegetative reproduction and dispersal by way of gemmae are known to occur in four types of fern gametophytes. Although they belong to basically tropical rain-forest genera, all four types have now been discovered growing natu rally in the vicinity of Highlands, North Carolina, as clones on shady, damp rocks. Their sporophytes were rare or absent. The gametophytes are now identified as Grammitis nimbata (Jenm.) Proctor, Grammitidaceae; Hymenophyllum tunbridg ense (L.) J.Sm., Hymenophyllaceae; Vittaria lineata (L.) J.Sm., Vittariaceae; and Trichomanes, probably representing several species, Hynmenophyllaceae. Identifi cation of the Grammitis was facilitated by the presence of some juvenile or dwarfed sporophytes; this constitutes the first report of this species, genus, and family for temperate North America. Growth and spread of fern gametophytes independently of, and distant from, the corresponding sporophytes is a novel phenomenon which should be investigated in other parts of the world.