He had been an artist and designer with the USPHS for 26 years. One of his paintings, which depicts president John Adams at Independence Hall signing the act that created the federal health service, is owned by the Public Health Service.
Mr. Jex was a prolific painter of landscapes, working in oils and watercolors. He went on painting trips in the Potomac and Shenandoah Valleys and in Europe, Canada and Mexico.
An authority on the Civil War, he painted pictures depicting that conflict and other historical subjects. These paintings and many of his landscapes were presented in exhibitions here.
Mr. Jex was as adept with the camera as with the paint brush. Shortly before the redevelopment of Southwest Washington, he and Dana Doten produced a documentary picture-story, "The Bulldozer and the Rose," tracing the history of that section of the city through architecture. The collection of photographs is owned by the Columbia Historical Society.
For many years, he painted portraits of outstanding athletes for the Touchdown Club.
Mr. Jex was born in Kent, Ohio. He grew up in Washington, and graduated from McKinley High School. After serving with the Army in World War I, he earned bachelor's and master's degrees in fine arts from George Washington University.
He was a medical illustrator for the Army Medical Corps, art editor of Nature magazine, and a free-lance artist and teacher before joining the Public Health Service.
Mr. Jex was a former president of the Arts Club of Washington and a longtime member of the Landscape Club of Washington.
He was a founding member of a group of Civil War enthusiasts, which he called "The Crackpates," which preceded the Civil War Round Table of Washington. He served as president of that organization during 1967-68. Earlier, he had received the Round Table's Gold Medal.
Mr. Jex, who lived in Arlington, also had received the Superior Service Award of the USPHS.
He is survived by a son, Garnet W. Jr., of St. Louis.