【英语时差8,16】自然人造花（在线收听）

There's nothing more artificial than artificial flowers, right?   Whereas real flowers have been around for millions and millions of years, artificial flowers are a purely human invention. They've been on this Earth only thousands of years, right? At any rate, you'd never expect to see an artificial flower growing in a wooded glen, right alongside its natural flower neighbors.

Well look again. There's a type of mustard plant, called "Arabis holboellii," which naturally grows a dainty, light blue flower atop its narrow stem. Without a doubt, these are natural flowers. But wait. Sometimes you'll see an Arabis holboellii sporting a bright yellow cluster of leaves that looks suspiciously like a buttercup. What's going on?

Those yellow leaf clusters are natural artificial flowers. What happens is this: The mustard plant gets infected with a type of fungus called "rust fungus." This fungus causes the plant to stop its natural flower production, and to produce a leaf cluster instead. The yellow fungus cells then gather along these leaves, providing the fake flower's artificial coloring. Just as natural flowers attract insects like bees and butterflies, these artificial flowers do too. In fact, the fungus produces a sugary liquid inside its fake flower that is ten to a hundred times sweeter than the nectar of real flowers.

Why does the rust fungus do this? Plants produce natural flowers to attract insects, which then cross pollinate the plants and help them reproduce. The fake flowers do the same thing for the fungus. Insects cross pollinate the fungus colonies, helping them reproduce . . . which leads to still more natural, artificial flowers!