A TINY plant is causing huge excitement among scientists - after fruiting for the first time in more than 130 years.

The plant, Nowell's limestone moss, is regarded as one of the world's most enigmatic and rarest, and in Britain it grows only in the Yorkshire Dales.

And the experts believe they now know why it is so rare - because the male and female plants are simply too far apart to breed.

The moss, zygodon gracilis, was last seen fruiting in 1866 by the amateur botanist who discovered and named it, John Nowell.

On the endangered species list, it was thought to exist only on two old sections of dry-stone wall in the Dales - until a team from the Natural History Museum and Bradford University set out to find and document the last remaining patches.

Botanists Dr Fred Rumsey and Dr Alistair Headley, found not only the moss but also the reason for its near-extinction on the slopes of Pen-y-Ghent - giving hope for its future recovery.

"Locating the moss was very exciting, but even more so when we realised it hadn't been able to reproduce successfully all these years because the moss patches, which are either male or female and mate via the spreading of spores, just haven't been close enough to each other to reproduce," said Dr Rumsey.

"Of the 500 moss patches we measured and recorded in the Dales, we found just one small area fruiting - a discovery that gives us a great opportunity to slow down, and possibly even halt, the extinction of a very interesting, but mostly overlooked species."

The museum and university are now collaborating on how to protect the plants from further decline and are carrying out molecular studies to see how they can bring the plants together.

When the team's research is complete they plan to move the mosses closer so they can reproduce and to teach the landowners how to care for the plant.