328 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
type were not made out, although this tvpe of wood was found in other 
petrified fragments from the same general horizon. Fig. 7 (PI. 32) 
is of particular interest because it shows in the upper part, in trans- 
verse section, one of the organs responsible for the scarred surface of 
the trunk. It is quite obvious that we have to do in this case with an 
appendage not of the nature of a leaf, on account of the cylindrical 
character of its trace. By looking carefully, by jjreference with a lens, 
at the lower part of the figure, it is possible to make out clearly that 
the organ just referred to is subtended by a leaf-trace. The organ in 
question is consequently clearly an axillary structure and either a root 
or a branch. An examination of its transverse section with the micro- 
scope makes it clear that it is not a root. Hence we must interpret it 
as of shoot value. It is in fact a short-shoot, as is shown by its failure 
to develop annual rings in the outer part of the trunk. Fig. 8 (PI. 
32) shows one of these short-shoots in transverse section at a point 
considerably farther out. The cylindrical character of the woody 
axis of the organ can be clearly made out as well as the absence of 
annual increments of growth. Fig. 9 (PI. 32) shows the appearance 
of the organs in question, very near to the surface of the trunk, under 
the same magnification as Fig. 8. It will be seen, that the pith and as 
a consequence the woody cylinder of the short-shoot have both become 
considerably larger. 
Not infrequently the short-shoots of this remarkable Gymnosperm 
branch in the course of their journey outward and sometimes at the 
surface of the trunk they are represented by as many as four or even 
five branches. This is all the more remarkable because there are no 
leaf-traces emitted from the cylinder of the short-shoot in their passage 
through the wood of the main axis, as is the case in Ginkgo biloba, in 
which I have observed a similar branching of the short-shoots within 
the wood of the parent axis. Ginkgo also differs from our genus in the 
fact that its short-shoots generally show the presence of annual rings, 
which are always absent in the type under discussion. The short- 
shoots apparently were lengthened in accordance with the thickening 
of the woody cylinder of the main trunk, through the activity of the 
cambium of the mother axis, exactly as is the case with the short- 
shoots of the living genus Pinus, in which the short-shoots persist in 
some species for a half a score or more years. 
The leaf-trace in our genus is also of considerable interest, because 
unlike the short-shoot, which it subtends, it has a limited duration and 
