for a ball full of little flies!"

"It's a very pretty ball, though," said Miss Harson, "with a smooth skin
and tinged with red or yellow, like a ripe apple. If it is cut open, a
number of granules are seen, each containing a grub embedded in a
fruit-like substance. The grub undergoes its transformation, and in due
course emerges a perfect insect. These pretty pink-and-white apples used
to be gathered by English boys on the twenty-ninth of May, which was
called 'Oak-Apple Day.'"

"Did they eat 'em?" asked Edith.

"I do not see how they could, dear," was the reply; "they were probably
gathered just to look at. Yet 'May-apples,' which grow, you will
remember, on the wild azalea and the swamp honeysuckle, are often eaten,
and they are formed in the same way; so we will not be too positive
about the oak-apples."

"What are oak-_galls_, Miss Harson?" asked Malcolm. "Are they the same
as oak-apples?"

"Not quite the same," was the reply, although both are produced by the
same insect. This is what one of our English books says of them: 'When
the acorn itself is wounded, it becomes a kind of monstrosity, and
remains on the stalk like an irregularly-shaped ball. It is called a
"nut-gall," and is found principally on a small oak, a native of the
southern and central parts of Europe. All these oak-apples and nut-galls
are of importance, but the latter more especially, and they form an
important article of commerce. A substance called "gallic acid" resides
in the oak; and when the puncture is made by the cynips, it flows in