4o8 
ALBAN STEWART 
cork layer usually forms on the outside, but one gall was found in 
which it had started to form below the periphery, cutting off some of the 
parenchyma. Stages between those shown in fig. i and text fig. i, 
show that the tissue towards the base of the leaf first becomes involved 
in gall formation. The tissue towards the base may be greatly altered 
while that at the apex is still normal. The resin cavity may become 
very much elongated so that it appears at a higher level in the gall 
than it would in the normal leaf. 
After having found a distinct stem structure in the young galls 
it is interesting to see what becomes of it in older galls. Fig. 3 is a 
diagrammatic drawing of a cross section made near the base of a gall 
near where the stem enters it. The stem has not become entirely 
enclosed by gall tissue at this point as a portion of the cork of the 
stem is still shown at k. The secondary bark tissue preserves many 
of its normal characters. The bast fibers occur in concentric rings, 
and there are sieve tubes and parenchyma layers between them. 
The bast rings are not continuous, however, as some of the fibers have 
been converted into parenchyma cells, a condition not dissimilar to 
what De Lamarliere (3) describes for the galls of Gymnosporangium 
clavariaeforme on stems of Juniperus communis. Bast fibers are 
entirely absent on the upper left side of the figure, while on the lower 
left side they are turned over nearly at right angles to their usual 
upright position. Occasional bast fibers are formed in the layers 
where normally only sieve tubes and parenchyma are developed. 
This is evidently not due to fibers being pushed out of place as they 
may occur where the bast rings are unbroken (see upper right side of 
figure) . 
The structure of the xylem is nearly normal except towards the 
upper side of the figure. The tracheids are here turned over more or 
less, and two multiseriate rays have formed in the wood. 
There is not much change in the woody portion of the cylinder for 
some distance farther in from the section shown in fig. 3. Two pro- 
jections appear after a time which develop into the condition shown 
in fig. 4. A large pith has developed in the center and two branches 
extend above and below. The one in the upper part of the figure is 
quite regular and presents many of the structures of a stem. A pith 
in the center is surrounded by wood in which there are rays extending 
outward into the somewhat modified secondary bark tissue (b) in 
which there are a few bast fibers distributed. The branch, which 
