Behind a gray house on a little street in West Cambridge, the asters and chrysanthemums are blooming in Mary Maples Dunn's garden. Herbs like tarragon and oregano grow in a small plot. Dunn often wakes early to tend the plants, her principal hobby.

"You're always transplanting and digging this up and putting that down," she says.

Dunn looks like your grandmother, with crisp white hair and a ruddy complexion, who stands just about five feet tall. She loves detective novels and just finished knitting a blanket for her first grandchild, who will be born next month.

When she resigned as president of Smith College in 1995, Dunn expected to retire to those pursuits full-time. When she changed her mind and accepted a post as head of Radcliffe's Schlesinger Library, she thought it would be her last job.

But now she might have her most challenging position yet.

The acting dean of the Radcliffe Institute for Advanced Study, who today becomes the only woman to head one of Harvard's 10 schools, Dunn will guide the new, $350 million Institute through its first critical days of self-definition.

Dunn comes to the helm after a long career in women's education. First a professor of colonial women's history, she became dean of Bryn Mawr College and president of Smith College, and later director of Radcliffe's Schlesinger Library.

At Radcliffe, where secrecy and closed doors have marked two years of negotiations, Dunn presents a striking contrast. She is easily accessible and friendly with students, having taught tutorials for history and literature concentrators and a first-year seminar.

"It was absolutely a delight to be able to work with someone as well versed as she is," said Cristin M. Hodgens '01, one of Dunn's students. "I think that she's really well suited to mentoring on every single level."