Past, present and future conspired yesterday to make the opening of this summer's Sunday dance festival at Glen Echo Park a picnic basket of very mixed quality.

The future was represented by two student groups. Five young women of the Glen Echo Apprentices looked as if they had put on auntie's airs as they slithered through "Povo," Sue Hannen's routine of show-biz styling and modern dance steps. More convincing were Raquel Pena's pupils from the Spanish Dance Center. They kept the dances moving between Pena's spitfire demonstration of the technical basis of flamenco and terse solos by Estefania Neira and Juan Valentin.

The state of the art was demonstrated by a troupe of movement improvisers called Talus, by Glen Echo's Betsy Eagan and by Chris Beavan's musicians. Talus might have been more fun to perform in than it was to watch. Beyond a few dispersals of bodies in space that resembled Kandinsky designs, only one brief passage looked vivid--David Appel's jerky, arm-swinging seizure as the baroque music began. "The Monkey God," Eagan's translation of a Far Eastern character into modern dance terms, was a good idea that was spoiled by the performance. Eagan caught the haunting, shrewd look of the role but lacked the nervous, technical brilliance. Besides the three professional Spanish dancers, it was the musicians who represented the best of the present. Beavan's neo-serialist "Grandpa's Gift" remained impressively somber despite a bit of clowning.

Films of great dancers of the past may be unfair competition for live performances. John Mueller showed rare footage from the University of Rochester archive: solos by intensely personal Mary Wigman and proud Harald Kreuzberg, a reconstruction of that fantasy of a rigid society that was Doris Humphrey's "With My Red Fires," and the final scenes of Leonide Massine's symphonic ballet "St. Francis." The driven Massine took the title role and Nini Theilade was a richly lyrical Lady Poverty in a new sound edition of this old rehearsal reel. Mueller, with great patience, has synchronized the dancing with a piano version of Paul Hindemith's score.