242 
J. L. WEIMER 
(191 5), after having studied the histology of these growths, concludes 
that they originate as modified axillary buds ; the leaf tissue becoming 
involved later. 
The writer's observations go to show that the cedar apples caused 
by this species usually break through the upper or inner side of the 
leaves, the first evidence of infection being the discoloration of the 
whole or a part of a leaf, followed later by a swelling usually from the 
upper surface but more rarely from the sides. The young galls grow 
rapidly and assume the characteristic shape and color very early in 
their development. It was found that when the infected leaves were 
removed the galls remained attached (PI. XII, Fig. i). This led to the 
belief that they must be in very close association with the leaf and 
perhaps originate from it. Specimens such as are pictured by Gid- 
dings and Berg (191 5) and Coons (191 2), where the galls are located 
near or even beyond the center of the leaf, were found in considerable 
abundance (PI. XII, Figs. 2 and 3). This strengthened the theory that 
these galls originate from the leaf. If these galls originated in the 
stem or as modified axillary buds with separate fibro-vascular systems 
it would be reasonable to suspect that in the very young stages at least 
the gall would be more firmly attached to the stem than to the leaf. 
A single gall has been found by the writer which has the appearance 
of having originated from the stem and it may be true that this mode 
of origin also exists, although it is certainly not the common method 
about Ithaca, New York. The writer has had the privilege of exam- 
ining young galls from West Virginia and Wisconsin and the method 
of origin herein described was also found in those galls. 
Before proceeding with a discussion of the internal anatomy of 
these galls a brief description of the structure of the healthy cedar leaf 
and stem will be given. The cedar leaf is attached to the stem through- 
out a large part of its length, only the apical portion being free. In 
cross section the leaf is triangular in outline at the apex but gradually 
becomes four-sided toward the base. The epidermis consists of a 
single layer of somewhat flattened, elongate cells with the outer wall 
covered by a thick layer of cutin. The epidermal layer on the upper 
or inner side of the leaf is broken by numerous stomata. Beneath 
the epidermal layer is a hypodermis on all the sides except the upper. 
For the most part this consists of a single layer of sclerenchymatous 
cells. This may however be reinforced at certain places, principally 
at the corners and in the region of the resin duct, by additional cells 
