Barber . — The Structure of P achy theca. II. 155 
are no such interspaces, owing to the greater mass of mineral 
deposited. In some parts of the section the structure is more 
broken up, and there the region of oval bodies is fairly 
definitely indicated. 
The outer part of the medulla, as would be anticipated 
from Fig. 5, is characterised by an interweaving of the 
granular threads ; and the region of the cortex is determined 
by the regularity of the spaced radiating tubes. Further, it 
is easy, in certain parts of the section, to trace the radiating 
filaments directly into the network of threads forming the 
outer part of the medulla (Fig. 8). 
In the figure I have drawn such a junction, — leaving out 
all the cracks and granules of the matrix. I have also used 
to the full the micrometer screw, in order to trace all con- 
nections of the filaments. At the same time this connection 
has not been exaggerated, for a general view of the prepara- 
tion gives a better impression of intimate union than the 
drawing of a few isolated filaments 1 . This is, I believe, the 
first specimen, if not the only one, in which cortical and 
medullary filaments have been seen to join one another. 
With regard to the branching of the filaments in P achy theca , 
a careful search in Sir Joseph Hookers specimens produced 
one or two cases in the outer portion of the cortex (Fig. B 4). 
The absence of well-defined cells in the present specimens 
has thus far prevented the detection of any cases of branching. 
In Fig. 8 there is a possible branching of the filaments, but 
such a case has not been certainly determined. 
Slide 10. Here, however, branching is by no means un- 
common. The slide contains a radial section, more or less 
resembling specimens 8 and 9 in the manner of preservation. 
The only traces of the cell-filaments consist in the granular 
threads already alluded to. While, however, the greater part 
of the pith and cortex is very poorly preserved, the section 
has all the appearance of containing the true periphery of 
the plant in a good state of preservation. 
1 In this specimen, as in slides 4 and 10, the nature of the section prevents 
photographic treatment. 
