802 THE AMERICAN NATURALIST. [ VoL. XXXIV, 
In dealing with the inner morphology of the galled leaf it 
was not thought necessary for the purpose of this paper to 
follow minutely all of the changes in the plant tissues during 
the development of the gall, but rather to observe the condi- 
tions of the tissues in well-marked stages of growth, and con- 
trast them with each other and with the conditions in normal 
leaves. 
L 
In the middle of February the young shoot representing the 
season’s growth of the branch is about 3 cm. long and consists 
of a central axis covered closely with leaf bundles, or fascicles. 
There are about seventy leaf bundles, or fascicles, to each 
young shoot. Each bundle is composed of a short secondary 
‘branch bearing three leaves, or “ needles," which are closely 
and completely enwrapped by several protective scales. The 
whole springs from the axil of the primary leaf (Fig. 1). 
Early in the season each primary leaf completely covers its 
leaf bundle, but by the middle of February the leaves begin 
to grow appreciably and soon stretch up above the tip of the 
primary leaf. At the tip of each young shoot there will be 
fascicles hidden by the primary leaves, while at the base of the 
same shoot these bundles may be twice as long as the pri- 
mary leaves, and between tip and base an intermediate condition 
may be found. At the time the gallfly is active the majority 
of leaf bundles are about 2 mm. in length. The length of the 
leaf bundle in relation to that of the subtending primary leaf 
and to that of the ovipositor is of great importance in connec- 
tion with the successful deposition of the eggs. 
To learn in what part the eggs were placed, the young shoots 
were examined in February, during the activity of the gallfly. 
The eggs were found deposited in masses on the outside of the 
youngshoot. They were placed, also, in great numbers between 
the leaf fascicles or between the primary leaves and the fasci- 
cles they subtend (Fig. 1, B), and it was thought at the time 
that the fly did not deposit the eggs in any other parts. The 
young shoots were examined to see if some substance, such as 
formic acid, were not deposited by the fly at the time the eggs 
