"Well, I suppose your mind will be at rest now," said Felicity. "What's that you have in your buttonhole?"

"That's a four-leaved clover," answered Peter exultantly. "That means good luck for the summer. I found it in Markdale. There ain't much clover in Carlisle this year of any kind of leaf. The crop is going to be a failure. Your Uncle Roger says it's because there ain't enough old maids in Carlisle. There's lots of them in Markdale, and that's the reason, he says, why they always have such good clover crops there."

"What on earth have old maids to do with it?" cried Cecily.

"I don't believe they've a single thing to do with it, but Mr. Roger says they have, and he says a man called Darwin proved it. This is the rigmarole he got off to me the other day. The clover crop depends on there being plenty of bumble-bees, because they are the only insects with tongues long enough to--to--fer-- fertilize--I think he called it the blossoms. But mice eat bumble-bees and cats eat mice and old maids keep cats. So your Uncle Roger says the more old maids the more cats, and the more cats the fewer field-mice, and the fewer field-mice the more bumble-bees, and the more bumble-bees the better clover crops."