Alternation of generations in ferns


Spore production is the asexual stage in the fern's life history. The plant producing the spores is called the sporophyte.

If spores land in a suitable environment, they germinate, and this marks the start of the sexual stage in the plant's life history, the plant produced is called the gametophyte.

(Move the mouse over the picture for label)

   
The image on the right was taken about 5 weeks after I sprinkled fern spores onto compost. With the naked eye, it looks as if the surface is covered with a green slime. Under the stereo microscope however, it is possible to see the gametophytes or prothalli. Move the mouse over the picture to see a magnified image of the prothallus, a heart shaped structure, on which the male and female parts of the plant can be found.

 

After several more weeks, the prothallus is more obvious and can be seen to have tiny rhizoids which absorb water and provide anchorage.

Below right is a living prothallus, about 2 months old and, on the left, one on a prepared microscope slide.

 

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