Moss Snorkels

WARNING: This information is inaccutate. Please see this more recent post for additional information.

Mosses along with all other plants need water, sunlight and air to live. However mosses don't have roots, which is the usual way that plants move water into their bodies. Instead they take up water from the environment through their outer layer of cells. They also exchange gases through this layer of cells. This causes a dilemma. Mosses have to drink and breathe through their "skin". Polytrichum commune and its close relatives have come up with a ingenious solution to this problem. They have snorkels. Okay they are not technically called snorkels, they are called lamellae, but that is what I like to refer to them as when I explain how they work. When the moss leaves are wet their entire surface is covered by a film of water. Gas exchange cannot happen through the water, but the snorkels stick out above the water and are dry at the tips to allow for gas exchange. The image that I posted is a section through a Polytrichum commune leaf, with the top side up and the bottom side down. The shiny white cells make up the thickened portion of the leaf and each green filaments of cells is a snorkel. Then wet, the spaces between the snorkels are flooded with water and the upper-most snorkel cell is exposed to the air. If you zoom in on this picture you may be able to see that the upper-most snorkel cells have a notch or divot in them. This is a microscopic clue that tells us this leaf is definitely from Polytrichum commune.