AN ANATOMICAL STUDY OF GYMNOSPORANGIUM GALLS 407 
cross section of this stem there is still another, which in lower sections 
has all of the structures of a normal stem. There are triangular 
wedges of xylem, leaf gaps, rays somewhat broader than normal, 
and a pith. Surrounding this is a region of secondary bark tissue 
resembling the normal in many respects except that the bast rings 
are poorly developed. In the section drawn the woody portion of the 
cylinder has become more or less broken up and the cells turned over 
but it still preserves enough of the original structure to show that it 
is a stem. In place of secondary bark tissue there are small paren- 
chyma cells instead. It should be noticed that a bundle leaves this 
modified stem on the upper side and extends into the gall. It is 
made up of two strands of scalariform tracheids, separated from each 
other the most of the way by a strand of parenchyma. This bundle 
is too large for a leaf- trace bundle, nor does it have the structure of 
such. It is more like that of a branch the central strand of paren- 
chyma probably being the pith. Branches are given off from this 
which run an irregular course. These branches are composed of 
scalariform tracheids which often have groups of other tracheids with 
bar-like thickenings in connection with them shown by X X X in the 
figure. Groups of similar tracheids occur in other parts of the gall. 
The epidermis ar^d hypodermis of the leaf is shown at e, on the upper 
side of the figure. This is the leaf from the axil of which the gall 
has arisen (see fig. i) the tissue of which has become involved in the 
formation of the gall since the stage shown in the figure just mentioned. 
The gall is surrounded by several layers of rather large cork cells. 
The remainder of the gall is of moderately thin-walled parenchyma, 
the cells of which vary greatly in size. What is evidently a part of 
the palisade tissue of the leaf is still preserved in the upper part of the 
gall, just inside the epiderm and hypoderm (e). The remains of the 
old resin cavity of the leaf is shown at r'. 
I have examined serial sections of a number of galls in about the 
same stage of development as the one shown in text fig. i, and have 
always found essentially the same structures. It was not always the 
case that as good a transverse section of the stem inside the gall was 
seen as the one shown in the figure, as that depends on the plane 
through which the sections are cut, and is largely a matter of chance. 
I was always able, however, to get enough in the sections to show that 
such a structure was present. The epidermis and hypodermis of the 
old leaf always appear, and usually some of the palisade tissue. The 
