"YOU'RE SURE THIS IS A RADISH" seems to be the thought running through mind of John Anthonisz as he holds up the latest in the series of oversized vegetables. The plant, which was grown at Old High Bluff by Syd Smith, 74 Main St. S., has a root two feet long, and foliage 20 inches long. It is five and a half inches in diameter at its widest part, and weighs six pounds, four ounces.