A Cretaceous Pityoxylon with Marginal Tracheides. 1 
BY 
IRVING W. BAILEY, A.B., M.F. 
Instructor in Forestry and Wood Technology at Harvard University. 
With Plate XXVI. 
I N their description of succiniferous Pityoxyla from the Cretaceous of 
Staten Island and Scituate, Jeffrey and Chrysler called attention to the 
fact that the wood of the pinelike Conifers of the Mesozoic, unlike that 
of the modern members of the genus, is characterized by the absence of ray 
tracheides. This condition was considered ancestral, inasmuch as among 
living pines ray tracheides do not occur in regions of phylogenetic significance, 
namely, the cone axis and the earliest formed wood of the stem. It was 
further inferred by the writers that the evolution of these structures, 
occurring in all probability in the Tertiary, explains the greater development 
of the genus in recent geological times. 
In view of this well-marked peculiarity of the pines which antedate the 
Tertiary, the occurrence of ray tracheides in a Pityoxylon from the Upper 
Cretaceous of Morgans, New Jersey, specimens of which have been sub- 
mitted to me for investigation, is of interest in affording a connecting link 
between modern pines and their Mesozoic ancestors. 
Anatomical Structure of ti-ie Specimen. 
The material in the form of lignite consisted of one large fragment, 
about 30 cm. long, 10 cm. wide, and 8 cm. thick, and several smaller pieces. 
The former, the core of a larger stem which had been flattened by lateral 
pressure, exhibited in selected areas an admirable state of preservation. 
A small lateral branch, which fortunately possessed a well-preserved 
medulla and brachyblasts or short shoots, was embedded in this fragment, 
and together with the other anatomical characters present in the lignite 
affords conclusive evidence of the affinities of the specimen. 
Fig. 1, PI. XXVI, shows the structural features of the larger fragment in 
transverse section. The annual rings are distinct and conspicuous, as is the 
1 Contributions from the Phanerogamic Laboratories of Harvard University, No. 41. 
2 Jeffrey, E. C., and Chrysler, M. A. : On Cretaceous Pityoxyla. Bot. Gaz., vol. xlii, July, 
1906, pp. 1-15. 
[Annals of Botany, Vol. XXV. No. XCVIII. April, 1911.I 
