324 Bailey . — A Cretaceous Pity oxy Ion with Marginal Tracheides . 
primitive Hard and White Pines, and the American Nut and Foxtail Pines, 
and the very primitive pine under consideration in this article the writer has 
been unable to find conclusive evidence in support of this theory. In many 
specimens of stem wood, conditions similar to those figured by Thompson 
were observed, but occurred invariably where the wood was of slow growth 
and twisted grain, and the tracheides in consequence of irregular shape. 
Root wood, as is well known, possesses an extremely short and twisted 
c fibre ’ which may account for the irregularly shaped tracheides found 
by Thompson in the root of Pinus Str obits and P. resinosa . 
Summary. 
t. In the identification of the remains of primitive Conifers the absence 
of alternate pitting, wood parenchyma, or ‘ Eiporen ’, or the presence 
of resin canals or ‘ Abietineenttipfelung ’ are insufficient data in determining 
whether we have to deal with a primitive member of the Araucarineae, 
Abietineae, or Cupressineae. 
2. The fact that bars of Sanio and ray tracheides are well-developed 
features of the lignite under consideration in this article indicates that 
we are not concerned with an Araucarian Conifer. 
3. The presence of short shoots and the general pine-like appearance 
of the fossil indicate strongly that the specimen is a primitive member of 
the genus Pinus . 
4. It is intermediate in structure between the older Cretaceous pines 
and the most primitive of living pines. 
5. It affords additional evidence that primitive pines possessed thick- 
walled ray parenchyma with piciform lateral ray pits, abundant tangential 
pitting in the summer tracheides, and highly resinous ray parenchyma. 
6. The somewhat infrequent occurrence of ray tracheides in the older 
portions of the stem and their entire absence from the younger wood 
indicate that these structures are of recent origin and are not strongly fixed 
upon the plant. 
7. The occurrence of ray tracheides in this Cretaceous pine indicates 
that the development of these structures occurred in the Upper Cretaceous, 
and not, as has been supposed, in the Tertiary. 
This investigation has been conducted in the Phanerogamic Laboratories 
of Harvard University, and to Professor Jeffrey the writer is indebted for 
material and kind assistance in the course of the work. To Professor 
Conwentz the writer is much indebted for his kindness in sending valuable 
material of the Baltic Pinus succinif era, and to Professor Jack of the Arnold 
Arboretum for material of Asiatic pines. 
