410 
ALBAN STEWART 
parenchyma cells usually accompany these in such a relation that one 
may assume that they are phloem cells, or cells that perform a similar 
function. Cells sometimes occur which are part parenchyma and 
part tracheid. They occur quite commonly in the gnarl-like com- 
plexes of cells in various places. As they are shown better in the next 
species, they will be considered further in that connection. 
After having considered stages in the breaking up of the stem in 
the gall as seen in transverse section, a longitudinal section will now 
be considered. Such a section is shown diagrammatically through the 
basal portion of a mature gall in fig. 6. The central cylinder of the 
stem which bears the gall is shown at c, which continues off at the 
upper left side of the figure. The two branches to the right constitute 
the central cylinder which enters the gall. This cylinder has a very 
broad pith {p) which begins very suddenly near where it joins the 
main stem. The bundles on each side of the pith have a tissue similar 
to secondary bark (6), in which there are strands of bast fibers. Rays 
occur among the tracheids of both bundles, and continue into the 
secondary bark as shown by the cross lines in the drawing. A portion 
of the old leaf is still attached to the lower part of the gall, some of 
the tissue of which seems still to be unaltered. The epidermis and 
hypodermis are shown at e, and the resin cavity at r, surrounded 
by the more or less modified parenchyma of the leaf. Immediately 
above the resin cavity there is a strand of tracheids with bar-like 
thickenings (/), such as always accompany the leaf-trace bundles. 
This branches and joins the base of the central cylinder entering the 
gall at about the same place that the leaf-trace bundle joins the 
central cylinder in the young gall shown in fig. i. There can be no 
doubt about this being a portion of a leaf-trace bundle especially as 
another leaf trace (/') leaves the central cylinder just opposite. There 
is an irregular mass of tracheids just above this strand, but whether or 
not it is made up of tracheids from the leaf trace, or is a branch from 
the main stem, I could not determine. The leaf trace bundle, in 
addition to the other bundles, is thus accounted for in a very young 
as well as in an old gall; so there can be no further doubt that the 
other bundles are derived from a stem. They are not leaf-trace bun- 
dles which have assumed the structure of a stem as was stated by 
Sanford. 
The remainder of the gall tissue consists of loosely arranged 
parenchyma cells which are surrounded on the outside by layers of 
