Louisa N. Plummer, 78, an expert horsewoman who spent her life in Chester County and lived on a farm in West Bradford Township, died of complications from ovarian cancer Monday, Nov. 22, at the Neighborhood Hospice in West Chester.

Born in Berwyn, Mrs. Plummer grew up in a prominent family in Devon. Her father, Thomas R. Neilson Jr., was an insurance executive; she told friends that he had stressed the importance of tending farm animals and pets.

As a child, all she wanted to do was ride. Her first official attempt was on the back of a black-and-white paint pony when she was only 3, according to the Driving Digest, a horse-related magazine.

Mrs. Plummer's real passion was fox hunting and showing her horses in local hunter shows, according to a statement issued by her caretaker on behalf of the family. In her early teens, she exercised horses for her father's friends, and in the 1950s regularly joined the Radnor Hunt. She hunted with groups as far away as Fair Hill, Md.

In the 1970s, Mrs. Plummer became interested in driving, the sport of guiding a horse hitched to a carriage or phaeton. She competed in driving events up and down the Atlantic seaboard.

Perhaps her favorite horse was a big Hackney-Clydesdale crossbreed named Mac. He was chestnut-colored, the caretaker said, and was often hitched to a wicker phaeton; Mrs. Plummer rode in the carriage, wearing a big hat. Together, they won the Old Guard class this summer at Walnut Hill, N.Y., the caretaker said.

Mrs. Plummer married Lavern E. Plummer when she was 40, the caretaker said.

She spent most of her time on her farm. She treasured her privacy and the company of her horses, sheep, and dogs.

When Mrs. Plummer became ill, the caretaker said, her Welsh corgi climbed up on her lap and "gave her a big hug."

Services are private.

Memorial donations may be made to the Neighborhood Hospice, 400 E. Marshall St., West Chester, Pa. 19380.