Holden. — Jurassic Coniferous Woods from Y orkshire. 541 
with two to five small piriform pits to each cross-field. Whether this 
Araucarioxylon represents the wood of the Araucarineae or not, it is 
impossible to say. If so, it must be almost the oldest fully developed 
specimen of that family. It seems much more probable that it belongs to 
Cordctites , whose presence in the Lias is vouched for by Lignier’s description 
of Artisia from that horizon (op. cit., ii, p. 135). 
Locality : Scarborough. Horizon : Oolite. 
Abietineae. 
Protobrachyoxylon eboracense (Figs. % 9 and 30). 
This specimen is among the most interesting lignites from Scarboro. 
The general features of the wood — small tracheides with predominately 
uniserial pits, thin-walled ray cells, and absence of wood parenchyma — may 
be seen in Fig. 29. When examined carefully, the radial pits of the tracheides 
are found to present certain peculiarities of structure quite unique in Coni- 
ferous woods. As stated above, the pits are usually in one row ; when 
two-ranked, as is not uncommon in the larger tracheides formed in the 
spring, they are always opposite. The uniserial pits are often scattered 
and circular, but equally often approximated and compressed. An example 
of the latter condition is shown in Fig. 30. Between the uppermost pit of 
the series and the one immediately below it may be seen on each side, but 
especially well on the left, a small white knob-like structure. Similar 
structures, though less well marked, may be observed below the next pit, 
and below the third they are quite evident again. Such appearances, which 
are exceedingly common in the best-preserved tracheides, can be interpreted 
as only one thing — degenerate bars of Sanio. To those who believe that 
the Abietineae are the ancestors of the Araucarineae, it is easy to see how 
these structures arose. As the pits of a Conifer like Pinus — remote, 
circular, and separated by bars of Sanio — become approximated, the bar is 
necessarily eliminated. It naturally disappears first in the centre, where 
the pits first come into contact with each other. As the pits become more 
crowded, only the ends of the bar persist. Such a condition is shown 
in Fig. 30. Occasionally, when the pits are not as closely approximated as 
usual, it is possible to make out a faint white line, connecting the knobs on 
the end. Such dumb-bell-like bars are very rare. In other places the 
centre of the bar is completely gone, but the ends, instead of being knob- 
like, are long and narrow. It is remarkable that these bars should persist 
when the pits are closely compressed, and not when they are scattered, but 
such is the case. In view of the fact that all transitional Araucarians, such 
as Brachyoxylon , &c., are descended from such a form as this, it is appropriate 
that it be called Protobrachyoxylon eboracense — the specific name to mark 
the place where it was found. 
