Like his art, Pollock's influence sprawled, blurring genealogical connections. Possibly Agnes Martin's grids are variants on Pollock's looping tangles of paint, though it's just as possible that her grids evolved from the geometries of Barnett Newman. Robert Ryman's all-white paintings calm the furor in Pollock's fields of light; also, they reverse the darkness rippling through the paintings of Clyfford Still. Who, then, are Ryman's aesthetic predecessors? Who are Martin's? Amid uncertainties like these, one line of descent is clear and fully documented. It leads from Pollock the father to Helen Frankenthaler the daughter, and on to a small band of painters who counted for a time as her younger brothers.