Judging by the size of the sacs, they were probably the large black/white/yellow garden spiders. But they should all have hatched by now and the babies flown away. You should see some of them in your yard and a few even should be lodging in your nandina. They are the ones who weave a large web nightly and have the zig-zag pattern in the center where they sit. The female will get very large, the males will remain small and after mating with the female will disappear, because she kills him. These are good spiders, but can still give you a painful bite so exercise care. Cheryl