“Fetch me a raw potato, Tom, please!
“Now,” Uncle George continued, “tell me what this potato is.”
“It is an underground stem,” said Frank.
“Yes! Why is it swollen? What do we use the potato for?”
“For food. Oh, I know,” said Frank, “it is a food store.”
Primrose.
Pilewort, showing Roots.
“Of course,” said his uncle. “It is a supply of food gathered up this year for next year’s plant. Look at the roots of the lesser celandine. I see Tom has drawn them. They are swollen. Are they roots, or underground stems?”