482 i Flora Unveiled
Heterospory: The Clue that Unified a KingdomHofmeister noted that the gametophyte generations of various ferns and “fern allies”^11
could be either monoecious or dioecious. For example, the prothallus of the fiddlehead fern
illustrated in Figure 18.2 is monoecious because both male and female sexual structures
(antheridia and archegonia) are present on the same prothallus. In contrast, the gameto-
phytes of the spikemoss Selaginella and the aquatic fern Marselia are dioecious because they
Figure 18.2 Diagram of the life cycle of ferns illustrating the alternation of generations.