Thursday, March 4, 2010

Liverworts on Springs


Liverworts are not, I have to admit, the most exciting plants - except when their spore capsules explode. These simple plants have been around for over half a billion years, confined to wet places like the muddy banks of streams, where I found this thalloid liverwort called Pellia epiphylla. Liverworts' common name derives from the fact that - if you've got a vivid imagination - their flat lobes look like lobes of green liver and since, according to the mediaeval Doctrine of Signatures, any part of a plant that looked like a part of the human body was supposed to be good for curing its ills, liverworts were assumed to be good for treating liver diseases. Superstition aside, liverworts become a little more interesting at this time of year when they produce these...
.. spherical spore capsules on the surface of the thallus. These change colour, from green to black as they ripen and then suddenly (for a plant) their stems elongate, often overight, raising the capsule aloft on a glassy stalk ....

.... then four vertical splits in the capsule wall become apparent and suddenly (this time, over the course of a few minutes) .....


... the capsule splits open, revealing a mass of green spores interspersed with strange whiskery golden threads.......

.... seen here at higher magnification.
You can see a short video of these writhing threads below .....



Here they are at higher magnification, along with a spore, and below....



... at higher magnification still, when it becomes apparent that each one of those golden threads, known botanically as an elater ...

.... has a helical spring embedded in it. Inside the ripe capsule the springs were all compressed but once the capsule wall splits their force is liberated, hurling out the spores until....

.... only 'springs' and a few remaining spores are left on top of the stalk. Meanwhile most of the spores...

... like this one, magnified here about 400 times, have been scattered to the four winds, to land on some muddy stream bank and germinate to form another thalloid liverwort. It's a cycle that's been going on for half a billion years and is repeated every spring.

11 comments:

  1. Brilliant! Another wonderful example of the extraordinary in the mundane. I had no idea about that elegant coiled spring design.

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  2. Have often seen Liverwort but never noticed the spore capsules so that is something for me to look out for in the future. Great illustrated explanation.

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  3. Brilliant! Thank goodness for the benefits of the microscope or we'd miss out on a lot of hidden glories.

    This is a fascinating post Phil and the pictures are wonderful. It's great to be able to see illustrations of how nature works.... things that we could never see with our own eyes. The helix spring is beautiful. :D

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  4. Absolutley fascinating post Phil.
    The magnified pictures of the elater are incredible.

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  5. Hi Nyctalus, the 'springs' can hurl the spores a considerable distance ... put a burst capsule on a sheet of white paper and it develops a broad halo of surrounding spores..

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  6. If you can find some Pellia and bring it indoors about now, John, the spore capsule stalks will usually elongate overnight - they grow to a height of about 5cm. then the capsules burst and the stalks collapse - it's all over in the space of a couple of days, so unless you're looking for it you tend not to notice...

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  7. Hi John, if you bring some Pellia indoors at this time of the year the spore capsule stalks will usually elongate overnight. they collapse again once the spores are shed, so the whole performance is over in a couple of days .... unless you happen to be looking for them, it's easy to miss the brief period of spore capsule production...

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  8. Hi Lesley, the helix is a lovely structure - especially if you view it in polarised light, when the thickened 'springs' show up in brilliant colours..

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  9. Hi Keith, I was amazed the first time I saw them.

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  10. Thanks once again, this has to be one of the best posts ever.
    I never cease to be amazed at what is going on under my nose, or feet in this case.

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  11. Thanks Adrian, I've long been fascinated by these ancient plants, ever since the first time I watched their slow-motion spore capsule explosion under a microscope.

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