208 Jeffrey . — On the Structure of the Leaf in Cretaceous Pines . 
of preservation. Much less of the base of the brachyblast is retained, 
and the sheathing bracts as a result present only a short segment. Above 
them, however, the foliage leaves are represented by much more elongated 
bases than in the last-mentioned figure. It may be made out that the 
fascicular leaves are more numerous than they are in any living Pine. 
Further, they are not in definite number as is the case in existing species of 
Pinus . The sheath in our specimen is composed of the same loose scales 
as are found in the sections Strobus and Cembra among living Pines ; but 
its component bracts, like the fascicular leaves, are much more numerous 
than they are in any living species of Pinus. Moreover they are not 
deciduous, as is true of the elements of the fascicular sheath in the sections 
Strobus , Cembra , & c. 
Fig. 3, PI. XIII, represents a transverse section through the bases 
of the fascicular leaves in another specimen. The section does not include 
all of the leaves of the fascicle, since some of these have been removed in 
process of fossilization. The second projection on the lower left side of the 
figure represents the growing point of the short-shoot, which, contrary to 
the conditions found normally in living species of Pinus> clearly persists, 
and in some of our specimens is protected by a covering of thin scale-like 
bracts. Regarding the remains of the growing-point of the specimen shown 
in cross-section in the figure as its organic centre, it is clear that there must 
have been more than twenty-five leaves attached to the uninjured brachy- 
blast. The number appears, however, to vary considerably, so far as we 
are able to judge from the rather fragmentary specimens at our disposal. 
As a result of the presence of a large number of leaves in the fascicles, these 
present, in the case of the internal leaves, a very different contour from those 
of the normal short-shoots of any living species of Pinus ; for instead of 
being bounded by either one or two plane surfaces and one curved one, as is 
invariably the case in the fasciculate leaves of existing Pines, the internal 
leaves in these polyphyllous brachyblasts are polygonal in outline and 
bounded on all sides by plane surfaces. Another feature of contrast to 
living Pines is presented by their phyllotaxy, for their fasciculate leaves are 
arranged spirally and not verticillately on the short-shoots. 
Before discussing further the internal structure of these interesting 
short-shoots, it will be well to refer briefly to impressions of a somewhat 
similar appearance described by other authors. Fontaine, in his monograph 
on the Potomac Flora, figures certain remains which he refers to Heer’s 
Jurassic genus Leptostrobus (‘The Potomac or Younger Mesozoic Flora’, 
Monographs of U.S. Geological Survey, XV). These he describes as 
presenting both fasciculate leaves and others, arranged spirally at intervals 
on the relatively main branches, the latter comparable to the primary leaves 
found in the seedling, and occasionally as the result of injury in the adult, 
of living Pines. The leaf-fascicles in Fontaine’s species are characterized, 
