He had given up all hope of finding it out for himself, and he could not plague his father about it when he was ill.

He had thought of the answer himself, but fancied it could not be the right one, for to see how it all fitted required some knowledge of physiology.

So, when he reached the end of his journey, he got down very quickly, and with his head just looking in at the window, said, as the gentleman gathered his gloves and newspapers: "Please, sir, can you tell me the meaning of a riddle ?" "You must tell me the riddle first," answered the gentleman, amused.
Diamond repeated the riddle.
"Oh! that's easy enough," he returned.

"It's a tree." "Well, it ain't got no mouth, sure enough; but how then does it eat all day long ?" "It sucks in its food through the tiniest holes in its leaves," he answered.

"Its breath is its food.