A previously overlooked painting by one of the Glasgow Boys has been rediscovered and will be included in a landmark exhibition to be staged at the Kelvingrove Art Gallery and Museum in 2009.

Last month The Herald highlighted the worldwide search that experts at the museum were conducting for the many "lost works" of the Glasgow Boys, the group of artists who transformed Scottish art in the late 19th century and paved the way for painters such as the Colourists.

The work, Spring Time at Moniaive, painted by James Paterson, is now to be shown in the major Glasgow Boys At The Kelvingrove exhibition, which is to be the first major retrospective of their work for more than 40 years.

The works of the group were collected by the rising industrial and entrepreneurial classes of Glasgow and inspired generations of painters. But since the late 1880s, when the painters such as James Guthrie, Paterson, John Lavery, George Henry were at their peak, many of their works have disappeared.

Now the work by Paterson, dating from 1887 and painted at his cottage, Kilniess, in Moniaive in Dumfriesshire, has come to light.

It was bought in a private sale by a Glasgow doctor in the 1990s. The doctor, who wishes to remain anonymous, saw the article in The Herald, contacted the Kelvingrove, and brought in his painting to show to the curators of the exhibition.

The bucolic work, a watercolour which usually hangs in the doctor's family home, has now been included in the show.

"I think it is great the public will be able to see the painting, rather than it just hanging in my house," the doctor said.

"I first saw it at a house in Edinburgh in the 1980s and admired it, but could not afford it. But eventually I bought it in a private sale from a man who did not like selling through salerooms: it was from an advert he put in The Herald, coincidentally.

"The curators at the Kelvingrove were very excited by it and said it was among the best painting of its type they had seen.

"They said it reaffirmed how good the Glasgow Boys were at watercolours as well as oil paintings." The painting, according to archives, was sold by the painter in the 1890s to a man named Galbraith for 25 guineas, and was at one point owned by a collector in Airdrie. But it has never been exhibited in public before. Hugh Stevenson, the curator of British art at the Kelvingrove, said: "As soon as we saw this watercolour we knew it was of the quality we were looking for. I can't think of ever seeing such a perfect watercolour by him.

"The date of this work, 1887, falls exactly within the period we are concentrating on in our exhibition, when the Boys were at the height of their powers and still painting in a recognisable style of their own. We'd be delighted if we could find more pictures of this quality in other collections."

James Paterson, who lived from 1854 to 1932, was the son of manufacturer Andrew Paterson.

He enrolled at the Glasgow School of Art before going on to study in Paris. He married, in 1884, Eliza Grier Ferguson, daughter of an engineer, William Ferguson. It was Ferguson's father who gave the newlyweds the cottage in Dumfriesshire where he painted a number of works.

Many works by the Boys - a loose grouping of around 23 artists who worked, lived or were connected to Glasgow in the late 19th century - have disappeared from view. Works such as Mademoiselle Cunegonde by William Kennedy, exhibited at the Glasgow Institute in 1885, have been lost.

Also missing are more than a dozen by John Lavery from the 1888 Glasgow International Exhibition, unique paintings of Glasgow by James Nairn, and most notably, a 5ft by 9ft work by Alexander Roche, called The Dominie's Favourites, a lifesized study of girls sitting on a bench, also exhibited in 1885.

Sometimes referred to as the Glasgow School, the painters - despite the name, not all from Glasgow - gained renown by irking the art establishment, primarily the Royal Scottish Academy in Edinburgh.

The Kelvingrove exhibition will focus on the period between 1890 and 1900.

Among the other missing works is Mademoiselle Cunegonde by William Kennedy, which was exhibited at the Glasgow Institute in 1885 and shows three girls in a garden.

Also lost is Playmates by George Henry, which appeared in Glasgow salerooms in the 1960s, was bought by a Scandinavian dealer, and never seen again.

James Nairn's unusual paintings of Glasgow, one of the Glasgow and District Railway, and one of a rainy West Regent Street have been lost.

The biggest loss, in scale, is a group of panels painted by the Boys for the 1888 Glasgow International Exhibition, they are huge paintings by Guthrie, Walton, Lavery and Henry.

Lavery made 50 paintings for the 1888 exhibition and one-third remain untraced and 10 or more pastels by Guthrie, which he made between 1888 and 1890 in Helensburgh, are still unaccounted for.

If you believe you know of undocumented or untraced works by the Glasgow Boys, contact Kelvingrove on 0141 276 9599 or write to The Herald.