160 Barber . — The Structure of P achy theca. II. 
bordered pits of Pinus (Fig. 5). In profile they appear 
as short black lines (Figs. 5 and 6). In the best specimens 
(Fig. 6) these appear to consist of two parts — a black line, 
and a distinct lens-shaped swelling at its centre : the lens- 
shaped mass probably appearing as the inner circle in surface 
view. 
The transverse walls do not completely bridge the spaces 
between the longitudinal walls in Fig. 6 — suggesting that only 
part of the transverse wall is preserved, or that the longitudinal 
wall itself has disappeared. 
6. The lacunae in the inner cortex, known as oval bodies , 
need not be present (specimens 9 and 1 1). This may explain 
the constant absence of such bodies in all the specimens 
examined from the transition beds between Silurian and Old 
Red Sandstone (Figs. B 8-14). In these specimens the dark 
lines are evidently comparable with the spaces between the 
radiating tubes of specimen 11. This similarity does away, 
at present, with the necessity for subdividing the genus 
Pachytheca. 
7. The specimen figured in Sir Joseph Hooker’s paper 
(Annals of Bot , III, PI. VIII, Figs. 3-7) I regard as indicating 
a condition of petrifaction not unmet with in the Cardiff 
specimens. In fact, certain parts of section 7 remind me 
strongly of it. The tubes, in these parts, are made up of 
elongated concretionary masses, separated by spaces of broken 
material (see Fig. 6) ; and the increase in number of these 
spaces gives the section the appearance of being composed 
of elongated parenchymatous cells. 
8. The branching in the cell-rows of the medulla is quite 
possible, although it is difficult to demonstrate (Fig. 8). The 
branching outside the region of oval bodies seems probable, 
seeing that the cell-rows are much nearer together in the 
middle zone than in the inner zone of the cortex. 
Undoubted branching has only been detected in the outer 
zone of the cortex, where it is characteristically present (Figs. 
9 and B 4). 
