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The Moss Lifecycle

The Moss Lifecycle 1

Referring to the diagram, the lifecycle of a typical moss can be explained by starting with the spores released from the moss capsule.

If the spore falls on to suitable ground, it starts to grow and develops into a small green shoot called a protonema.

This protonema soon grows buds that become the familiar leafy green stems of a moss. This phase of the moss  lifecycle is termed the gametophyte.
 
The Moss Lifecycle 2

Within some leaves of the gametophyte, special structures develop into male and female sex organs.

The male part is called and antheridium and the female part the Archegonium

Inside the antheridium, sperm are produced. They possess tails which allow them to swim, in a film of water, to the archegonium.

They are attracted to the archegonium by chemicals released into the film of water.

Once reaching the archegonium they swim down its neck to reach and fertilise the egg within.
 
The Moss Lifecycle 3

The now fertilised egg develops into a structure called the sporophyte. The sporophyte consists of a stem or seta and a capsule in which vast numbers of spores are produced.

During the growth period when the seta is elongating and the spores growing and maturing, the capsule is protected by a thin covering called the calyptra.

When the spores are nearly ripe, the calypra falls off revealing a cap or operculum that keeps the spores from being released.

Finally, when the spores reach maturity , the operculum falls off and, usually in dry weather, the spores are shaken out of the capsule and dispersed by the wind.

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This project was funded by the RIAS Millennium Awards Scheme