Jeffrey. — On the Structure of the- Leaf in Cretaceous Pines. 219 
tissue closely related to the centripetal wood and resembling that found 
in some Cordaites. 
4. The name Prepinus is proposed for this type in the belief that it is 
the direct ancestor of Pinus. 
5. Many of the true Pines of the Middle Cretaceous possessed the 
same double transfusionary foliar sheath as is found in Prepinus , but 
entirely lacked the centripetal wood which is characteristic of that genus. 
6 . The elongated pitted elements described by Worsdell and others on 
the ventral side of the protoxylem in existing Coniferous leaves appear 
rather to be relics of the inner transfusion sheath, which is a feature of 
Cretaceous Pines, than of true centripetal xylem. 
7. The Abietineae are the oldest living family of the Coniferales. 
8. Pinus is the oldest living representative of the Abietineae, and has 
in all probability been derived from Prepinus , which shows many archaic 
features. 
In closing, the writer wishes to offer his best thanks to Dr. Hollick of 
the New York Botanic Garden, in whose company most of the material here 
described was collected. He also wishes to express his indebtedness to 
Professor F. W. Oliver, of the University of London, for the opportunity of 
examining unique preparations of Cordaitean leaves. 
DESCRIPTION OF PLATES XIII AND XIV. 
Illustrating Professor Jeffrey’s Article on the Leaf of Cretaceous Pines. 
PLATE XIII. 
Fig. 1. Surface view of a short-shoot of Prepinus statenensis. x io. 
Fig. 2. Transverse section of fascicular leaves of Prepinus statenensis. x 13. 
Fig. 3. Surface view of short-shoot of Prepinus statenensis. x 10. 
Fig. 4. Fascicular leaf of Prepinus statenensis. x 40. 
Fig. 5. Leaf-bundle of attached fascicular leaf of the 'same, x 100. 
Fig. 6. Axis of the brachyblast of Prepinus statenensis. x 18. 
Fig. 7. Part of the wood of the brachyblast of Prepinus statenensis. x 180. 
Fig. 8. Upper part of the woody axis of a brachyblast of Prepinus statenensis. x 20. 
Fig. 9. Tracheids of axis of brachyblast of Prepinus statenensis. x 180. 
Fig. 10. The same, x 500. 
Fig. 11. Detached leaf of Prepinus statenensis. x 64. 
Fig. 12. The same, longitudinal section of the xylem. x 400. 
Fig. 13. Detached leaf of Prepinus statenensis. x 30. 
Fig. 14. Bundle of Prepinus statenensis in transverse section, x 140. 
Fig. 15. Part of the same, x 500. 
Q 
