Dr. Jay C. Bryant, 78, retired research chemist at the National Cancer Institute of the National Institutes of Health and an early specialist in techniques of growing massive cell cultures, died April 10 at his home in Silver Spring after a heart attack.

A native of Susquehanna County, Pa., Dr. Bryant moved to Silver Spring in 1940 after receiving a bachelor's in soil science from Pennsylvania State University and a master's in soil science from Cornell University. He held a doctorate in biochemistry from Georgetown University.

Dr. Bryant was a soil scientist with the Department of Agriculture from 1940 until 1947 when he joined the tissue culture laboratory at the National Cancer Institute as a research chemist. He was author and coauthor of numerous papers contributing to developments and techniques in the field of cell growth in vitro.

His marriage to Mary Marquette ended in divorce.

He was a member of Sigma Xi, an honorary society of chemists; the American Chemical Society; the Tissue Culture Association; the American Society for Cancer Research; the American Society for Cell Biology and the Soil Science Society.

Survivors include his wife, Jean B. of Silver Spring; a sister, Marion Smith of Springville, Pa., and a brother, Carlton F. of Boynton Beach, Fla.