4o6 
ALBAN STEWART 
rows of parenchyma, which is covered on the outside by layers of cork 
cells {k). The leaf trace bundles are shown at /, two of which leave 
the woody cylinder (c), about opposite each other. Immediately 
above the leaf-trace bundle, on the right side of the figure, there is 
another bundle which is given off from the woody cylinder of the 
stem and extends to the base of the gall. Figure 2 is a diagrammatic 
drawing of a longitudinal section of a young stem and of an axillary 
bud (hd). Towards the lower part of the figure the central cylinder 
gives off two leaf-trace bundles (Z), which go to a pair of opposite 
leaves. Just above the place of departure of the leaf- trace bundles, 
the central cylinder of the stem divides. One of the branches goes 
off to the right as a continuation of the stem, while the branch to 
the left enters the base of the young bud {hd). The similarity between 
figs. I and 2 is so great as to leave no doubt about the origin of the 
gall, as the vascular systems are the same in each case. The gall 
can be nothing more than an abnormally developed axillary bud, 
but whether or not it is a bud transformed I am unable to state 
definitely. It seems likely that the fungus has stimulated the develop- 
ment of a bud which from the start is transformed into a gall. I have 
examined a number of galls, in about the same stage of development 
as the one shown in figure i, but have failed to find in any of them 
an indication of embryonic leaves, such as would probably be the 
case if the bud were already formed when the infection took place. 
In the witch's broom on this same species of juniper, caused by 
Gymnosporangium juvenescens Kern, the development of buds is 
greatly stimulated. It is not unreasonable to suppose that a some- 
what similar condition exists here in regard to bud development. 
After having considered to some extent a longitudinal section 
of the vascular system of a very young gall, it seems well to consider 
the cross section of a somewhat older gall and of the branch that bears 
it. Such a section is shown semidiagrammatically in text figure i. 
A cross section of a normal leaf is shown in the lower part of the figure 
with a leaf trace bundle entering it. The leaf trace is flanked on 
each side by rows of tracheids with bar-like thickenings, shown by 
X X X in the figure. A portion of the base of another leaf is shown 
to the right, while the gall occupies the upper part of the figure. 
Just above the section of the lower leaf is the cross section of the 
stem that bears the gall. The heavy lines represent the rings of 
bast fibers, which are absent on the side next to the gall. Above the 
