210 Jeffrey. — On the Structure of the Leaf in Cretaceous Pines. 
the true centripetal wood, as has been maintained by Worsdell, and more 
recently by Bernard and others. 
Before turning our attention to the structure of the higher portion 
of the leaf in the species under consideration, it will be well to examine 
briefly the organization of the axis of the short-shoot. Fig. 8, PI. XIII, 
shows the manner in which the large traces of the fascicular leaves pass 
from the central cylinder of the brachyblast. It is to be noted that they 
do not divide into two, as is the case in the primary leaves of the seed- 
ling even of the Strobus group of Pines. This is additional evidence that 
we have really to do with a short-shoot and its appurtenant leaves. Fig. 6 
shows the structure of a section through the woody cylinder of the short- 
shoot of the same specimen which furnished Figs. 2, 4, and 5. The 
magnification is not sufficient to show the details of structure ; but it 
is possible to make out that there are islands of sclerenchyma, appearing as 
dark spots in the pith. This feature is not found in living representatives 
of the Strobus and allied sections of living Pines ; but is common among the 
Hard Pines with three and five fascicular leaves. Fig. 7 shows a portion of 
the woody cylinder of the short-shoot more highly magnified. Although 
the enlargement is considerable the tracheids appear small. The most 
important feature of this figure is the presence of a resin-canal in the upper 
portion stopped with tyloses. The presence of this phenomenon in the 
wood of a shoot showing but a single annual ring makes it certain that 
we can have to do with nothing but the axis of a deciduous shoot or 
brachyblast. Thus the histological structure of the axis of these curious 
leafy shoots, which we have named Prepinus statenensis , makes it clear that 
they are brachyblasts of a primitive and somewhat generalized type of 
Cretaceous Pine-like Conifer. 
In view of the general tendency to regard the Araucarians as the most 
ancient Conifers, the radial pitting of the tracheids of the brachyblasts 
in this species is of special interest. Fig. 9, PI. XIII, represents the ends 
of several tracheids of Prepinus statenensis as seen under a magnification of 
180. It is to be expected, if the Araucarineae really represent the most 
primitive type of Conifer, that some evidences of Araucarian structure 
should be found in the wood of this ancient Pine-like Conifer. The 
crowded pitting in the ends of the tracheids is purposely chosen for 
our Fig. 9, since one might expect to find the flattened or angular 
Araucarian type of pit exemplified under these conditions if at all. It will 
be noticed, by examining the figure, that the pits do not become more than 
slightly oval as a result of extreme approximation and in no case show the 
angularity or flattening of the Araucarian type. Fig. 10 shows the pits 
very highly magnified, to enforce the truth of this statement. On the left 
can be seen indications of the presence in the walls of the tracheids of the 
folds of Sanio between the adjacent pits, especially in the lower part of one 
