"Neither did I," said Susie. "I just know if I plant mignonette, mignonette will grow; and if I plant sweet peas, sweet peas will grow. That's all I ever thought about it."
"Would you like to know?" asked Uncle Robert.
"Oh, yes," said Susie.
"How can we?" asked Donald. "The seeds are in the ground, and we can't see them."
"If Susie is willing to dig up one of her sweet peas," said Uncle Robert, "perhaps it will tell us what it has been doing since she planted it last week."
"Oh, yes," said Susie. "See if you can find one, Don. I put lots in."
Down on their knees went Susie and Donald, and began digging in the soil.
"Here is one," said Donald, "just ready to come up, and another close to it. The tip of it must have been through. See, it is green."
"Wouldn't it be green in the ground?" asked Susie, looking closely at the tiny plant.
"Why, no," said Donald. "Things are never green when they're covered up. It's light that makes things green. Don't you know how yellow the grass gets if a board lies on it, and what yellow stalks the potatoes have when they sprout in the cellar? It must be the light that makes them green."