Mosses in the Polytrichaceae spread their spores in a really neat way. Shown here are Atrichum sporophytes. Another member of the family that I have blogged about is Polytrichum, which also shares this dispersal mechanism.
Atrichum's manner of spores dispersal has been described as a salt shaker mechanism. And as you can see on the up-close shot below, it is a pretty good analogy. The mouth of the capsule is surrounded by a ring of short, immovable teeth that attach to a disc covering the opening to the capsule. The disc keeps rain from entering the capsule so that the spores do not start to grow before they have exited the capsule. When a breeze or a passing animal jostles the capsule the spores sift out from between the teeth. This mechanism also keeps the spores from coming out in a single mass, which would pretty much defeat the ability of these spores to spread on the wind.
If you are ever out in the woods and see some Artichum (or Polytrichum) sporophytes, give them a tap. You may be rewarded by a poof of spores emanating from the top of the capsule.
Fun Fact: Spores are so small and light that they can disperse very long distances. Researchers carried out a study (I am not sure of the reference off the top of my head, but I will check.) where they attached sticky microscope slides to the wings of a plane that flew high into the air. What do you know, they found moss spores all the way up in the the jet-stream. Pretty cool that they are able to travel that far up and then far away!
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