Five picture books worth on look; A Bear in the Air, by Leslie Williams. Owings Mills, Md.: Stemmer House. $7.95

Have you ever stretched out in the warm grass on a summer afternoon and watched big white clouds tumble through the sky? One boy who does sees a bear in the air. As it happens, the bear is in need of repair, so that boy, Mordecai , climbs a handy rainbow and finds the bear's paw is caught in a trap. He frees him, mends the bear's tear, and stays on for a visit. Alistair, the bear, has an annoying habit. He ends every sentence with a word which rhymes with "bear." Mordecai helps him ovewrcome this peculiarity before falling off the could and riding a sheet of rain back to earth. It's go od fun for little ones who like to make rhymes.