I find Jackie in the garden, digging holes with a stick in a section of the flowerbed that's gone to weeds. "Whatcha doing, kiddo?""Planting dinosaur seeds," she says, beaming up at me. She uncurls her fist to show me five dull pebbles, each one slightly elongated so it bears a faint resemblance to an egg.She's four, so I play along, crouching beside her. "Oh, yeah? What kind of dinosaurs are going to grow from those?"She giggles. "It's a mystery!"Jackie soaks up vocabulary like a sponge. "Mystery" is one of her new favorite words."Do you remember what we learned about plants?""They need lots