Mosses with Moving Teeth

We had a couple classes in the Evolution of Green Plants laboratory that I am teaching which focused on mosses. During lab we looked at some mosses that have arthrodontous peristome teeth. (arthro- meaning joint & -dontous referring to teeth) The joints and thickenings of the cell walls enable the teeth in many mosses to move in response to changes in humidity. In the species shown here, the teeth are closed when wet and open when dry. This allows the spores to be dispersed from the capsule when the conditions are optimal for them to fly on the wind to distant locations.

In this moss, we added water to the peristome. Then with the tip of a paper towel we removed the water and watched the magic happen. This specimen is under a dissecting scope, hence the funny circular view, and I used the video function on my digital camera to record it. I cannot recall the species name of this moss. I am pretty sure it is either in the genus Ulota or Orthotrichum, both in the Orthotrichaceae.

Thanks to Dr. Goffinet for bringing in this moss and helping to make this video.