Igo BOTANICAL GAZETTE [OCTOBER 
cells. These cells have their long axes extending vertically, and 
are wider tangentially than radially. 
Anatomy of gall 
Gross ANATOMY.—Many galls were examined and were found to 
vary considerably in size. The largest one measured was 3.5 cm. 
in diameter, and the smallest one had a diameter of 0.5 cm. They 
vary in shape from ovoid to globular, and usually encircle the stem. 
Ordinarily the galls appear singly, but it is not unusual to find them 
very close together or even confluent on the stem, and characteristi- 
cally at the nodes. The outer surface of the gall is roughened much 
more than the outer portion of the normal bark, either above or 
below the hypertrophy. There has been such a development of 
suberized tissue on the periphery of the gall, due to the presence of 
the disease, that it becomes broken into deep, irregular, longitudinal 
' fissures (fig. 5). 
Pycnidia of Macrophoma are scattered irregularly over the sut- 
face of the gall. These pycnidia are flask-shaped, and are imbedded 
in the parenchymatous tissue of the gall. They have a pseudo- 
parenchymatous wall and open to the exterior through an ostiolum. 
The pycnidia are barely visible to the naked eye, and are more 
abundant in the region of the fissures. Considerable sloughing of 
the bark from the surface occurs, especially at the time of the 
increased activity of the cambium region in the spring. 
It is interesting to note the enormous increase of the hyper- 
trophied part of the stem in comparison with the apparently normal 
stem above and below the gall. No less interesting is the macro- 
scopic comparison of the normal wood and bark of the region below 
with the region through the gall (fig. 8). It shows to advantage the 
relative amount of increase of the tissue in question, as a result of 
the stimulation of the pathogene. The averages, obtained from the 
measurements of twenty-five galls of various sizes, are as follows: 
Radius of galls... .. a ee eee 10.5 mm. 
Rachie OF wood OF Gals... i ee. 7.0 
‘Thickness of bark of gallg. 0.2, 3.5 
Radius of stem immediately below gall.......... 5.0 
Radius of wood immediately below gall.......... 4. 
