214 Jeffrey. — On the Structure of the Leaf in Cretaceous Pines. 
counterpart of Worsdell’s 4 peridesmic transfusion tissue \ Through the 
kindness of Professor Oliver I have had the opportunity of examining 
the beautifully preserved material upon which Miss Stopes’s observations 
were made. Fig. i< 5 , PL XIV, shows a leaf-bundle from this material some- 
what highly magnified. The fibrovascular strand is surrounded by a 
cordon of large, apparently empty cells, which constitute the outer or 
‘ peridesmic ’ transfusion tissue. The centripetal xylem lies on the upper 
side of the bundle, within the ‘peridesmic’ sheath just described. The 
bundle illustrated in Fig. 16 presents in essential features a striking resem- 
blance to Fig. 14, the most marked differences being the presence of 
centrifugal xylem in Prepinus , and the fact that the inner sheath of the 
transfusion tissue does not extend over the posterior region of the xylem in 
Cordaites. In the sections loaned by Professor Oliver there was a good 
deal of variation in the extent of the inclusion of the centripetal xylem by 
the inner thick-walled transfusional sheath, in some instances there was 
only a single tracheid between the mass of centripetal xylem and the 
large-lumined outer sheath of transfusion tissue. In any case there is 
a very striking resemblance between the foliar bundles in Prepinus and 
Cordaites. This resemblance is none the less significant because of the 
opinion frequently expressed in recent years by competent investigators, 
that the Coniferales are descended from the Cordaites or from a Cor- 
daitean plexus. 
In Fig. 17, PL XIV, is shown a section through the basal region 
of a four-leaved fascicle of a contemporary Cretaceous Hard Pine. The 
needles are surrounded by the close membranous sheath of the Hard 
Pines and have the double leaf-trace which is characteristic of that 
group. By examination it will be seen that the leaves are without 
resin-canals in the basal region shown in the figure, and in this respect 
conform to the fascicular leaves of living Pines and differ from Prepinus 
statenensis described above. The double bundles of the leaf-traces are 
surrounded on the outer side in the region of the vanished phloem as well 
as in the region of the xylem by a sheath, comparable to that found in 
Prepinus statenensis. This sheath sends off a tongue which is inserted 
between the two bundles, forming a complete septum of separation. Fig. 18, 
PL XIV, shows the structure of a detached leaf from a Cretaceous Pine with 
a two-leaved fascicle. It is highly probable, from the presence of double 
bundle in the leaf in question, that it represents a Hard Pine. In Fig. 19, 
PL XIV, appears in transverse section the leaf of another species of bifoliar 
Pine which is characterized by the presence of a single fibrovascular bundle 
and consequently in all probability belongs to the general group of Soft 
Pines. In both these figures it is to be noted that the transfusion tissue is 
of the same type as in Prepinus statenensis, being composed of an inner 
dense sheath and a broad zone of outer large lumined transfusion elements. 
