Under a harvest moon last night, a tent in the Decatur House garden on Lafayette Square was full of autumn flowers matching the brick terrace. It was an elegant evening planned by the Decatur House Council of the National Trust for Historic Preservation to honor Edith Cummings Munson, who gave $500,000 to remodel the old Decatur House stables and carriage house bordering the garden.

The 108 diners, many of them with hair to match their pearls, were [Old Washingtonians who] included Dudley Brown, designer of the Decatur House garden; Caroline Simmons, a former Decatur House Council chair; and Adm. John Kane, who served on the Truxton-Decatur Naval Museum board.

They sat at round tables covered with padded cloths, the settings laid out with a ruler to ensure just the right distance between wine and water glasses. Dinner began with shrimp bisque and progressed through stuffed veal to trifle.

Munson, whose donation was made in honor of her late husband, Curtis, spoke after dinner, carrying her audience to a time when war was an adventure and her husband was a dashing naval hero and intelligence officer. She remembered when her father-in-law lost $24 million overnight in 1929 and his son--her husband--made a good bit of it back.

She said that Curtis Munson served Franklin Delano Roosevelt as an intelligence officer, "but Roosevelt didn't like to listen," so Munson had to tell one of FDR's aides everything. She remembered what it was like to be a World War II Red Cross volunteer, one of a small group of women on a ship with 15,000 male troops. And she recalled that after sharing a cabin with 24 women on her way to London, her husband met her at the dock with the promise of a room for two at Claridge's.

After her speech, she said, laughing, "Oh, I forgot half the stories I was going to tell. Weren't my friends lucky?"

Michael Ainslie, head of the National Trust, said that Munson's gift would help make Decatur House self-supporting, an aim of the Trust in the face of decreased government funding. The remodeled building, according to Earl James, Trust properties administrator here, will be used to expand Decatur House programs by providing exhibit space and leasable conference and ballroom space.