Serena Williams extended her Grand Slam winning streak to 18 matches by beating Aleksandra Wozniak 6-1, 6-2 Monday in the fourth round at the French Open. Playing the first match on center court, the No. 2-seeded Williams advanced in 53 minutes. She committed only eight unforced errors while totaling 25 winners to nine for Wozniak. Williams is seeking her 11th major title and third in a row.