1. Fern Prothallium with Antheridia and Archegonia: The prothallium of a fern, also known as the gametophyte, is a small, green, heart-shaped structure that arises from a spore. One of its key characteristics is the presence of antheridia and archegonia. Antheridia are the male reproductive organs that produce sperm, while archegonia are the female reproductive structures that house the eggs. Both of these organs are located on the prothallium’s surface and facilitate the fertilization process. The prothallium is typically flat and photosynthetic, ensuring it has the necessary energy to support reproduction and development.
2. Fern Embryo on Prothallium: Once fertilization occurs, the fusion of sperm and egg leads to the formation of a fern embryo. The embryo develops within the archegonium, and as it grows, it becomes attached to the prothallium. This attachment is crucial since the prothallium provides nutrients and support during the early development of the new sporophyte. The fern embryo represents the initial stage of the sporophyte generation and will eventually grow into a mature fern.
3. Fern Young Sporophyte on Prothallium: As the embryo continues to develop, it transforms into a young sporophyte. This young sporophyte will begin to grow leaves and roots, forming a distinct diploid phase in the fern life cycle. Initially, the young sporophyte may still be connected to the prothallium and relies on it for sustenance. Over time, as it matures, it will become independent, develop more complex structures, and eventually produce spores that will continue the life cycle.