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 the YouTube clip below for more detailed information.
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| Cyrtomium fortunei sori, made up of spore-producing sporangia |
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| Cyrtomium fortunei - aka Holly Fern |
One fern that I grow,
Dryopteris filix-mas 'Euxinensis has just had to be repotted as its roots were pushing through the bottom of the pot. And what roots! It's hardly surprising as this robust fern can get quite big and my idea is to have it as a kind of statement, on a stand of some sorts eventually.
Seeing that the Cyrtomium was producing spores, I took a look at the undersides of the leaves of Dryopteris filix-mas 'Euxinensis' (commonly known as the 'Male Fern'), and noticed that it too has produced spori which are actually smaller than those of the Cyrtomium. If you click on any of the images you should get a closer look.
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| Dryopteris filix-mas 'Euxinensis' sporangia |
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| Dryopteris filix-mas 'Euxinensis' |
You might find this YouTube clip, about the sex-life of ferns, interesting:
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