Charles Drechsler, 93, an authority on fungi who retired from the Department of Agriculture in 1962 with 45 years of federal service, died of cardiac arrest Wednesday at the Heritage Health Care Center in Takoma Park, where he had been for about a month.

Dr. Drechsler's subject was mycology, the branch of botany dealing with fungi. He identified numerous previously unrecorded fungi during his career at Agriculture, most of which was spent at the Beltsville research center. Many fungi are poisonous or harmful to other plants and his drawings of them were as well known as his descriptions of them.

Over the years, he published more than 100 papers in professional journals. He was a fellow of the American Phytopathological Society and a member of numerous other professional bodies, including the Botanical Society of America, the Mycology Society of America, the Washington Botanical Society, the Washington Academy of Sciences and the Wisconsin Academy of Arts, Letters and Sciences.

In 1958, he received the Distinguished Sevice Award from the Department of Agriculture.

A resident of University Park, Dr. Drechsler was born in Butternut, Wis. He received bachelor's and master's degrees from the University of Wisconsin and then went to Harvard University, where he received a doctorate in mycology in 1917.

He moved to Washington that year and joined the Agriculture Department. Except for a brief period of Army service during World War I, he remained with the department until he retired.

Dr. Drechsler was a member of the University United Methodist Church in College Park.

Survivors include his wife, the former Mary Florence Morscher of University Park; three children, Charles Drechsler of Burlingame, Calif., Kathryn Finnegan of Flemington, N.J., and Robert Drechsler of University Park; seven grandchildren and one great-grandchild.