THE FASCINATING SEX LIFE OF FERNS
Ferns are sporophytes with fascinating sex lives. I noticed the other day that the undersides of my Cyrtomium fortunei fronds are studded with sori (singular - sorus), individually called sporangium (pl. sporangia). Each individual sporangium contains spores. When the spores fall and germinate they produce tiny gametophytes (prothallus) which are quite unlike the parent plant. These gametophytes then produce on their surface male sex organs (antheridiums, which in turn produce flagellate sperm) and female sex organs (archegonium, which produce an egg). The sperm reaches the egg by swimming through water which is certainly one good reason why ferns like damp conditions, and together they form a zygote: a diploid, i.e. containing two complete sets of chromosomes! The zygote then forms a young sporophyte on the surface of the gametophyte. At least, that is how I understand it. See th...