Mary Summerfield Gardiner, 85, a professor emeritus of biology at Bryn Mawr College and the author of two textbooks on biology, died of congestive heart failure April 1 at Georgetown University Hospital.

Dr. Gardiner, who was born in Garden City, N.Y., graduated from Bryn Mawr in 1918. She spent the next three years at the Henry Street Settlement House in New York City and then returned to Bryn Mawr as a warden, or resident faculty member, in one of its dormitories. She received her doctorate in biology at the college in 1927 and joined its faculty as an instructor.

She was named chairman of the department of biology in 1941 and was promoted to full professor in 1949. In the course of her work, she organized the design and construction of a new biology building, the cornerstone of which was laid in 1958.

On her retirement in 1965, Dr. Gardiner was made a professor emeritus. She also received the Lindback Award for excellence in teaching.

Dr. Gardiner's books included "The Principles of General Biology," which was published in 1952 by the MacMillan Co., and "The Biology of Invertebrates," which was published in 1972 by McGraw, Hill. At her death, she was working on a book about the biological discoveries of the early explorers.

When she retired, Dr. Gardiner moved to McLean, where she lived with her sister-in-law, Mrs. Arthur Z. Gardiner. From 1969 to 1975, she was a resident associate in invertebrate biology at the Smithsonian Institution. In recent years she also had recorded books for the blind.

Survivors include a sister, Mrs. Julian Burgess of Pennington, N.J.