The fern gametophyte stage starts from the unicellular haploid spore until the formation of the multicellular prothallus containing the antheridia and archegonia. In our experiment, we germinated Christella spores in tissue culture medium and observed them weekly. They are very pretty to look at especially under the microscope. The stages of fern gametophyte development for Christella are spore, formation of rhizoid and prothallial initial, protonema stage, spatulate stage, heart stage, and lastly the mature prothallus. Then if fertilization takes place, a growing sporophyte could be seen from the heart of the prothallus. Here are some photos I’ve taken mostly under microscope. I do not have pictures for the first three stages though.
There were only a few prothallus germinated in my Petri dishes so they were really big like miniature lettuces! After this semester break, maybe I’ll pay a visit to our tissue culture room hoping they are still there.