And buy!  Gardeners are allowed to browse the hundreds of perennials laid out at the Bridge of Flowers Plant Sale - but no touching!  Not until the starting bell rings out.  This year the young woman in charge of the Annuals from LaSalle's in Whately said for the first time she had two women poised over a single flat of gorgeous rich purple geraniums. They did not come to blows; they shared, half and half. The sale runs…