"They are not apples such as we eat, or fruit in any sense," said her governess. "They are the work of a species of fly called _Cynips_, which is very apt to attack the oak. 'The female insect is armed with a sharp weapon called an _ovipositor_, which she plunges into a leaf and makes a wound. Here she lays her eggs; and when she has done so, she flies away and we hear no more of her. But the wound she has made disturbs the circulation of the sap. It flows round and round the eggs as though it had met with some foreign body it would fain remove. Very soon the eggs are in the midst of a ball-like and fleshy chamber--the most suitable provision for them, and one which the parent-insect had provided by means of puncturing the leaf. As the eggs are hatched the grubs will find themselves safely housed and in the midst of an abundance of food.'"