100 SPENCER : THE AFFINITY OF DADOXYLON TO CORDAITES. 
pith of Dadoxylon is composed of a number of flat saucer-like 
discs formed of cellular tissue, these in the fossil state form the 
transverse bars of Sternbergia. Although I have had the pleasure of 
examining Prof. Williamson's specimens and of reading his descrip- 
tions, yet having discovered some very good specimens myself it 
will be more convenient for me to describe the character of Dadoxylon 
from my own specimens. 
Dadoxylon. transverse section. 
In a transverse section of the stem the pith is seen to be much 
larger in proportion to the woody zone than that of recent pine 
stems. The hexagonal cells of the pith are clustered together in two 
or three portions of the pith area, so that nothing striking is seen 
in its character in a transverse section. The narrow woody zone is 
seldom marked by those concentric rings which are so conspicuous 
in modem pines, and the bark is rarely preserved. 
LONGITUDINAL SECTION. 
The Sternbergian character of the pith is very conspicuous in 
a long section. The pith is seen to be composed of a number of 
shallow disks formed of cellular tissue, and when these became com- 
pressed and the intermediate spaces filled in by calcite, &c, there is 
left the peculiar transverse markings of Sternbergia. The long section 
also shows us the character of the wood cells of the woody zone, and 
also that of the medullary rays and the areoles or the equivalents of 
the pitted ducts of the true pines, which occur in two or three rows 
on the long wood cells. It will be seen from the above description 
that a longitudinal section of a plant is as equally important in 
determining its structure as a traverse section. 
It is a very rare thing to find a Dadoxylon enclosed in its 
cortical layer, and consequently very few fossil botanists even are 
acquainted with its real character. One of my sections which is 
about two inches in diameter, shows a small part of the outer 
portion of the bark, which is composed of very delicate cells, and 
if the whole area of the cortical tissue was composed of similar 
cells we need not wonder at the rariety of its preservation. This 
is the largest and thickest branch or stem that I have hitherto met 
with showing structure. The pith, which is of the usual discoidal 
