Reproduction and dispersal
Typical view of gametophyte – caught in torch-light, a bright dark-green felty blob hanging from the roof of a small sandstone cave, Arran.
Spore production varies greatly throughout the range of this species and diminishes to the north, although even the most northerly known sporophytes in the world, on the Kintyre coast in Scotland, have been seen to produce some spores. The rather globose-triangular spores are shed green. Less than 40µm in diameter, the thin walled spores cannot withstand strong desiccation and must germinate rapidly, but in wet winds could, and almost certainly have been widely dispersed from the areas of its greatest abundance on the Atlantic islands up the western seaboard of continental Europe.
The resulting gametophyte can be very locally dispersed from its point of arrival through fragmentation and by its production of gemmae – vegetative propagules borne on specialised funnel shaped cells, the gemmiphores. These may be distributed by small invertebrates moving through the colonies, or be water borne in damp trickles. They are unlikely to move far but play a role in re-colonisation of prime sites and maintenance of the plant in an area. Molecular work has however established that some British gametophyte clones exist over several kilometers (Rumsey, et al., 1999), which given the poor dispersive powers and slow growth rates indicate a considerable antiquity.