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I N T R O D U C T I O N
The life cycle of a fern
Most ferns are homosporous, meaning that they produce a single type
of spore. After a fern spore settles in a favorable place, 2 it develops into a small, heart-shaped
gametophyte that sustains itself by photosynthesis. 3 Each gametophyte has both male and female sex organs,
but the archegonia and antheridia usually mature at different times, ensuring cross-fertilization between
gametophytes. 4 Fern sperm, like those of all seedless vascular plants, use flagella to swim through
moisture from antheridia to eggs in the archegonia and then fertilize the eggs. 5 A fertilized egg develops
into a new sporophyte, and the young plant grows out from an archegonium of its parent, the gametophyte. 6 The
spots on the underside of the leaves (sporophylls) are called sori. Each sorus is a cluster of sporangia.
7 Sporangia release spores, which give rise to gametophytes (Campbell et al,
1999).
Ferns can also be used to illustrate the
variation between homosporous and heterosporous plants. Each system features
differences in the life cycle of vascular plants. The diagram below should help
contrast the two:
What About
Pollen?
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