Scientists are studying the genetics of a rare moss which has "flowered" for the first time in more than 130 years.

Nowell's Moss is found on old limestone walls in the Yorkshire Dales and has declined as the walls have deteriorated. It does not produce flowers as such, but develops spores after reproduction between male and female plants.

Although clumps of the moss have been found across the Yorkshire Dales, they have either been all female or all male, and too far apart for reproduction to take place, leaving the plant an endangered species.

However, for the first time since 1866 - when it was discovered by botanist John Nowell - researchers have found the endangered moss with fruiting bodies, on the slopes of Pen-y-ghent Hill, in the Yorkshire Dales.

Dr Fred Rumsey, UK plant biodiversity researcher at the Natural History Museum, was one of the botanists working on the project.

"I was absolutely overjoyed when we found the flowering moss, because I knew the history of the plant and I knew that the last person to see this was a famous botanist in the 1860s," he said.

"The moss had a really unusual distribution and was only known to grow on limestone walls, which made us consider where it grew before man. We also don't know why it won't grow on new limestone walls.

"We looked at literature on the plant and found out the areas where it had grown in the past, and then we went back to those sites and extended the search from there, and we found it on several of those old sites.

"It was still abundant in small areas in low altitudes, but some of the colonies were all one sex and there were no opportunities for them to reproduce.

"In some of the sites, there were both sexes, but they were a metre or two apart and that may not seem far but for a very small sperm that is a long way to swim. They need a continuous stream of moisture. Therefore, the plants cannot successfully colonise and so stopped reproducing sexually."

Scientists from the University of Bradford and the Natural History Museum are collaborating on how to protect the plants from further decline. They are carrying out molecular studies and looking at genetic variations to see how they can bring the plants together.

They are also studying small mites that have been damaging the plants by eating the female sex organs.

When their research is completed, they plan to move the mosses closer to one another so they can reproduce, and to teach the farmers who own the land where the moss lives how to care for it, to ensure its future survival