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How does a bryophyte zygote develop into a sporophyte?

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Thick green bryophyte moss covers the trunks of three oak trees in a forest, with fallen leaves on the ground. — bryophyte Bryophyte moss growing on oak trees.

In bryophytes, the development of the sporophyte begins following fertilization, when a sperm nucleus unites with an egg nucleus within the archegonium to form a diploid zygote.1

The zygote remains inside the archegonium, where it undergoes numerous mitotic cell divisions to develop into an embryonic sporophyte. During this process, the lower cells of the archegonium also divide to form a protective structure known as the calyptra, which sheathes the growing embryo.1

As the sporophyte enlarges, it remains physically and nutritionally dependent on the gametophyte. The developing sporophyte maintains an intimate connection with the gametophytic tissue through its base, or foot, which remains embedded in the gametophyte to absorb water, minerals, and nutrients. Eventually, the mature sporophyte produces a sporangium to release spores, completing the alternation of generations.12