What Is a Tree?

All that day, Zirro couldn't think about anything else. Every time he rolled past a recycling bin, he put his hand on the little hatch in his chest to make sure the unknown object was still there.

That evening, as he stood beside the fountain, a voice said, "Zirro! Why are you talking to your tummy?"

It was Dana, a nine-year-old girl who lived in Tower One Hundred and Twelve. She had two puffy pigtails and always wore a yellow raincoat, even though it never, ever rained in the City of Glass. Every evening Dana sat on the edge of the fountain and told Zirro about her day at school, and Zirro listened and made little noises that meant I understand.

Zirro opened the hatch in his chest and showed her the unknown object.

Dana gasped and clapped her hands over her mouth. "Oh my goodness... it's a seed!"