12 THE OAK 
ripening of the former. At the more pointed free end 
of the acorn is a queer little knob, which is hard and 
dry, and represents the mummified remains of what was 
the stigma of the flower, and which lost its importance 
several months previously, after receiving the pollen. 
The outer hard coat of the acorn is a tough, leather- 
brown, polished skin, with fine longitudinal lines on it, 
and it forms the outer portion of the true covering of 
the fruit, called the pericarp (fig. 2, p). On removing it 
we find a thin, papery membrane inside, adhering partly 
to the above coat and partly to the seed inside. This 
thin, shrivelled, papery membrane is the inner part of 
the pericarp, and the details of structure to be found 
in these layers may be passed over for the present with 
the remark that they are no longer living structures, 
but exist simply as protective coverings for the seed 
inside. 
The centre of the acorn is occupied more or less 
entirely by a hard brown body—the seed—which usually 
rattles about loosely on shaking the ripe fruit, but 
which was previously attached definitely at the broad 
end. A similar series of changes to those which brought 
about the separation of the acorn from the cup— 
namely, the shrivelling up of the tiny connecting 
cords, &c.—also caused the separation of the seed from 
the pericarp, and we may regard the former as a dis- 
tinct body. 
Its shape is nearly the same as that of the acorn in 
which it loosely fits, and it is usually closely covered with 
