Monday, November 22, 2010


To appreciate the true beauty of mosses you really need to explore them with a hand lens or low power microscope. This is Tortula muralis, wall screw-moss and to find out how it acquired that colloquial name you need to take a close look at the spore capsules.

Wall screw moss grows in the mortar-filled cracks in walls, where it produces spore capsules that are carried aloft on stalks that are a couple of centimetres long at maturity. These are capsules in the very early stages of development, before their stalks lengthen, but if you take a really close look at a mature spore capsule.... looks like this. Notice how the capsule's stalk (seta) has twisted helically. If you take a close look at the capsule (double click on the image for an enlarged version) you can see that most of it is sheathed in a membranous covering - the calyptra. Gently pulling this off with a pair of forceps reveals....
 ... a lidded capsule underneath and if you pull the lid (operculum) away....

... it reveals a screw thread-like arrangement (the peristome) underneath, that gives the moss its common name. These threads twist up tightly in moist air but untwist in a dry atmosphere, allowing the minute spores to be shaken out when the seta trembles in the wind. In this image you can see that the operculum that has been removed has become temporarily stuck to the base of the capsule - normally it will just fall away.


  1. Dear Phil, just to let you know that this info is fascinating and appreciated. I feel I am just starting to learn about the natural world. Such similarities between superficially(?) different species such as mosses and humans. cheers, catmint

  2. Another interesting and informative post Phil. Thanks for sharing.

  3. This is a wonderful blog and ofcource, I stated loving botony after watching all these photographs. I will recommend this blog to botony students in my acquaintance. Really informative and uncommon. Thanks for your great work

  4. Wonderful blog and your closeups open up a world that many of us can't record on our day-to-day cameras.

  5. Hi David, You can see moss peristome teeth with a x10 hand lens so I wonder if it's possible to photograph them by holding the lens in front of the camera lens.........?


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