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J. L. WEIMER 
as stated above and as it continues to develop from year to year it 
becomes firmly attached to the twig, appearing to have originated in 
the twig (PL XV, Fig. 5 and PI. XVI, Fig. 3). 
In case of the above mentioned infected leaves where there was 
scarcely any swelling, the infection presumably took place in the 
summer of 191 3 but was not apparent in the late summer or fall of 
1914 and first became obvious in the spring of 1915. That the fungus 
had been developing in the leaf for some time seems certain when it is 
considered that in nineteen days after the trees were removed to the 
greenhouse telial horns had been produced. For some unknown reason 
the characteristic stimulation of cellular activity did not occur and 
when the mycelium reached the spore-bearing age, spores were pro- 
duced. 
Other cedar trees brought into the greenhouse early in the spring 
of 1914 produced cedar apples during the spring of 1915. These were 
scarcely more than telial horns coming directly from the leaf as in the 
other cases described. These were probably infected in the fall of 
1 91 3 and the mycelium was able to live in the leaf from that time until 
the spring of 1915, or approximately two years before causing any 
noticeable effect on the host. 
These small galls developing on the leaf at considerable distance 
from the stem seldom reach any great size, probably due to their 
distance from the stem and a consequent lack of sufficient vascular 
tissue development. 
A study of a large number of serial sections through the stem and 
young gall shows a condition such as is apparent in Plate XVI, Figures 
1, 2, and 3. Plate XV, Figure 7, shows a section of a cedar leaf which 
had a slight discoloration but almost no swelling. The leaf when sec- 
tioned was found to be permeated with mycelium. A corky exterior 
layer K is already being developed in the gall shown in Plate XVI, 
Figure i. The resin duct r is present and the vascular bundle is the 
leaf-trace bundle somewhat enlarged. Figure 2 shows much the same 
condition. Figure 3 illustrates a still more advanced stage. In this 
section the tip of the old leaf still remains visible at the apex and the 
corky exterior covering is well developed. The gall has become closely 
attached to the stem similar to the condition found in old galls where 
the stem tissue is probably also involved. 
