SPENCER : THE AFFINITY OF DADOXYLON TO CORDAITES. 101 
character and occupies a relatively smaller area than that of any 
other of my specimens, ir rather more than a quarter of an inch in 
diameter. This is enclosed by the woody zone (composed of fine 
wood cells) of about half-an-inch in radius. This woody zone shows 
six or seven rings of growth, and appears to have been about as much 
above the normal proportion of area as the pith falls short of its 
normal proportion. In other words, the woody zone appears to have 
increased in area at the expense of the pith area. Surrounding the 
woody zone is a zone now occupied by calcite, which has evidently 
taken the place of the bark, of about a quart er-an-inch in diameter. 
Surrounding this zone there is a thin zone of very fine and thin 
walled cellular tissue, which appears to be either part of the bark or 
the inner edge of the epidermal layer, but the outer layer of that 
tissue is not represented in the specimen. Whether the zone of 
calcite and thin wall of cellular tissue represent the full width of the 
cortex cannot be determined from this section, but it shows us that 
the fundamental tissues occupied a large proportion of the area of 
the stem much larger than they occupy in the stems of recent or 
fossil pines. 
In Witham's work on " The Internal Structure of Fossil Vege- 
tables," there is a very good section of a cycad ( Cycas revoluta ) in 
which the fundamental tissues are seen to occupy a large part of the 
stem, while the woody tissue, which is of a very lax description, forms 
a narrow zone dividing the area of the large pith from the broad 
cortex. 
Had Witham been acquainted with the full meaning of this 
peculiar feature of the structure of the Cycadese, as illustrated by his 
own section of Cycas revoluta, it is not improbable that he would have 
seen that his supposed pine stems were more nearly allied to the 
cycads than to the pines. But there were two facts in connection 
with Pinites, which he does not appear to have been acquainted with, 
namely, the discoidal character of the pith and the large area occu- 
pied by the cortex. Although the discoidal nature of the pith 
would not have aided him in fixing the affinity of the fossil plants, 
because it appears to be a structure dependent upon rapidity of 
growth, and is found at the present day in plants of widely different 
