I N T R O D U C T I O N
The life cycle of a moss
The gametophyte is the prevalent generation in the bryophyte cycle, a characteristic that contrasts with other plants. 1 Most species of moss have separate male and female gametophytes, which have antheridia and archegonia, respectively. 2 After a sperm swims through a film of moisture to an archegonium and fertilizes the egg, 3 the diploid zygote divides by mitosis and develops into an embryonic sporophyte within the archegonium. 4 During the next stage of development, the sporophyte grows a long stalk that emerges from the archegonium but the base of the sporophyte remains attached to the female gametophyte. 5 At the tip of the stalk is a sporangium, a capsule in which meiosis occurs and haploid spores develop. When the lid of the sporangium pops off, the spores scatter. 6 Spores germinate by mitotic division, forming small, green, threadlike protonemata (sing.:protonema) resembling green algae. 7 The haploid protonemata continue to grow and differentiate, eventually forming sexually mature gametophytes, completing the life cycle (Campbell et al, 1999).
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