The Simple Life.(Kate Bosworth)(Interview)

Byline: Photographed by Mario Testino.

Why an actress's effortless, pared-down chic is irresistible to today's hottest designers. Sally Singer does the New York collections with Kate Bosworth.

On a single afternoon in the fall, Kate Bosworth visited one talented young American designer after another--each of whom was frantically preparing for the spring collections. Bosworth wore an electric-blue strapless dress with a single dart in the front, which is to say, a Jil Sander skirt by Raf Simons that the actress had hiked up to add yet more edge to an already edgy separate. On her feet were strappy flats from Chloee, and on her shoulder hung, a little demurely, an ivory leather Marc Jacobs bag that was an It bag: One of the hazards of being Kate Bos worth is that every bag you carry automatically becomes an It bag. That bag was tossed onto the long refectory table (itself suddenly an It table as a consequence) in the Chinatown studio of Proenza Schouler. At the Met's Costume Institute Gala six months before, Bosworth had knocked out Jack McCollough and Lazaro Hernandez (and indeed le tout New York and le tout fashion world) with a silver Prada dress and marcel-waved hair--a look both fabulously flapperish and ultra-up-to-date. It was mutual friendliness at first sight, and the designers joined Bosworth and her boyfriend, James Rousseau, for an after-party drink at the Beatrice Inn. "They called the next day and asked if I'd be their date for the CFDA awards," she remembers. And she was their date, in a restrained feathered sheath, and they were the Designers of the Year of 2007 (jointly with Oscar de la Renta). Little wonder, then, that she found herself invited back to preview (and bring luck to) their spring collection, and she was happy to oblige: "The fashion world feels more normal to me when I'm with them."

If anybody thinks that she's just beautiful and game, they're failing to recognize the difference between a pretty girl in a pretty dress and a muse

While a very tanned and sinewy Erin ("Honey, I'm running 20 miles a week to prepare for a marathon") Wasson walked for the designers in a drum-majorette-on-safari suit, Bosworth carefully surveyed the photographs of the upcoming looks. Feathers featured, naturally, and plastic plumage, and chiffon cut to look like something feathery.

"Your CFDA dress took us in a whole different direction," Hernandez happily admitted. "I feel that feathers can sometimes be an older thing," Bosworth remarked. Hernandez answered, with a laugh, "We love taking stuff from an old lady's closet and giving it to you." He added, more seriously, "Everything is really personal for us--this transition between growing up and being young, being a grown-up and being wild."

Then it was time for Bosworth to transition out of the Proenza Schouler loft, jump into a car, and zoom off to Chelsea. There, at Derek Lam's studio, the actress admired a streamlined peasant dress in vivid emerald and a red silk dress that reminded her of "a little tulip." Lam became enamored of Bosworth after meeting her at a Tod's event in Los Angeles. "She's so down-to-earth, and yet she's already made an iconic movie." He was speaking, of course, of Blue Crush, in which the then nineteen-year-old actress put, one can safely say, a new spin on the Gidget story.