Barber . — The Structure of P achy theca. II. 153 
drawn, in my former paper, to the thickness of the stopper- 
like transverse walls (see Figs. B 3 and 4). Although in those 
sections we had to do with well-preserved longitudinal walls, 
yet, in cases of difficulty, it is easier to follow the regularly- 
placed short black lines than the tubes themselves. Thus, 
upon a careful examination of section 1, with the high power 
(Fig. 1 a), there may be seen such a transverse wall in the 
branched radiating tube just beneath the point of bifurcation. 
And the presence of this small black line is sufficient to 
determine the question so often asked with regard to Sir 
Joseph Hooker’s slides, ‘ Do the medullary filaments pass 
between or into the oval bodies?’ 
Slide 7 is selected from an interesting batch which Mr. 
Storrie has prepared since my examination of the specimens 
so far described. It contains an accurately radial section, 
and the cells of the cortex are in a similar state of preserva- 
tion to that of Slides 5 and 6 . In the present case, however, 
the cortex is unique, in that everywhere along the radiating 
tubes, the short black lines are marvellously distinct (Fig. 6). 
On the other hand, I cannot detect one double circle. It is 
worth while, in passing, to note the curious fact that, here, 
as in the former cases, the black lines do not stretch right 
across the tubes. This may indicate that only a median part 
of the transverse wall is preserved. However this may be, 
the absence of similar longitudinal walls shows that, in the 
living plant, the characters of transverse and longitudinal 
walls differed. 
Slide 8 (Fig. 7). This section differs very greatly in ap- 
pearance from those on the slides so far dealt with. It 
corresponds in direction with those on Slides 2 and 4, being 
a tangential section through the cortex. 
Under a low power the section appears to consist of 
numerous tubes with dark brown, granular contents, and 
very thick clear white walls, — in fact, the resemblance to a 
transverse section through the stalk of a living seaweed with 
mucilaginous walls, such as Polyides or parts of Laminaria , 
is very striking. 
