412 
ALBAN STEWART 
gall, made near where the gall joins the main stem, is shown diagram- 
matically in fig. 8. The relative position of this section in the gall 
is about the same as the section of G. juniperi-virginianae shown in 
fig. 3. The magnification of this figure is much higher than is that 
of fig. 8, so that the central cylinder is much wider at the start in the 
glohosum gall. What is evidently very much modified tissue of the 
secondary bark is shown at h, which is not well differentiated on the 
right and left sides of the figure. Bast fibers are fewer in number 
as can be seen by comparing the two figures just mentioned. A 
median longitudinal section of a portion of the stem bearing the gall 
is shown at c, the pith being the stippled portion in the center. Tra- 
cheids radiate outward above and below, and in the center of the figure 
they take an irregular course next to the secondary bark tissue. 
Sections taken a little deeper often show strands of tracheids running 
through the modified pith tissue (fig. 9) which often surround broad, 
ray-like masses of parenchyma. They may continue for some time 
and then disappear resulting in the condition shown in fig. 9. Sec- 
ondary bark tissue is fairly well differentiated in this section and 
can be seen entirely around the cylinder. The tracheids take a very 
irregular course inside of this, but in places there are wedges of xylem 
which show a true transverse structure. They are shown by the tri- 
angular area covered with cross lines in fig. 9, and one is shown under 
high magnification in fig. 12. This wedge presents what appears to 
be three distinct rings of growth, as there are three bands each of 
spring and summer wood alternating with each other. Whether or 
not these are true annual rings I do not know. As this gall is perennial 
in growth, and as secondary thickening takes place in both of the 
galls being considered in this article, it is not unreasonable to suppose 
that they are true rings of growth. If they are rings of growth they 
are better developed, where they occur, than in the galls of G. juni- 
perinum where, according to Wornle (11), growth rings are poorly 
marked. 
The woody cylinder widens deeper in the gall as can be seen by 
comparing figs. 8 and 9. The greatest diameter in the gall figured 
is nearly 5 mm., but galls were examined in which it was more than 
8 mm. The cylinder finally breaks up and branches out in the gall, 
but preserves a semblance of a stem structure much deeper than in 
the gall of G. juniperi-virginianae previously considered. 
The origin of secondary stem structures in the gall is shown in 
