What's hiding in the undergrowth of Rachel Ruysch's bold and beautiful flower painting? This is a world where buds hiss like snakes, poppies twirl and tiny insects devour - a vibrant, fecund jungle, full of uncanny life. Cathy FitzGerald hears how this great Dutch artist was influenced by her unusual childhood as the daughter of Frederik Ruysch, maker of one of the world's great curiosity cabinets.