Sunday, November 22, 2009

Polypody – the fern with the golden sporangia

Some polypody Polypodium vulgare ferns continue producing spores deep into winter and if you turn over a few fronds you’re eventually likely to find these golden cluster of sporangia. Unlike many ferns, the sporangia of this species are not covered by a membrane during their development and under the microscope they resemble nests of golden eggs, or maybe even party balloons if you're in a celebratory frame of mind.

Each sporangium is packed full of spores and when they’re ripe there’s a remarkable mechanism for catapulting spores out into the airstream, that you can read about at

The gaping sporangium at the top of this picture (above) has burst open and has already catapulted out most of its spores. You can still see the spores packed into the surrounding unripe sporangia, through their transparent walls 

Polypody spreads vegetatively with creeping rhizomes, that either grow over the branches of trees or through old walls, and you can see it in its habitat over at


  1. Reminds me of caviar, too. ;-) Gorgeous photos.

  2. I read that as 'polyploidy'. Three times. Until I noticed it didn't even make grammatical sense...

    Been working with cell cycle stuff too long already methinks!

    Wonderful photos! I like how you zoom in gradually, rather than throwing extreme close-ups at people without context =D

  3. Thanks Wilma. You've clearly got expensive tastes!

  4. Thanks for your kind comments Psi Wavefunction, Interesting that you should mention polyploidy... it triggered a dim recollection and had me reaching for the textbooks... to discover that there's an allopolyploid series of Polypodium species in Europe
    P. vulgare 2n= 4x=148 (AABB)
    P. interjectum 2n = 6x=222 (AABBCC)
    P. australe 2n=2x=74 (CC)
    .. and I've learned (all because of a near- anagram)that ferns go in for speciation via auto-and allopolyploidy rather a lot. Thanks!


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