Telangium (Calymmatotheca) showing Structure . 163 
outline of which is not very clearly defined, but can be seen to contain 
tracheides of narrow lumen, v. Fig. 4 c. These are best seen rather 
to one side of the section, and possibly occupy one arm of a V-shaped 
strand. 
The whole section is limited by the large-celled epidermis with 
blackened contents ; within this are groups of thin-walled cells which have 
broken down, and at / the section has passed through the lacunar tissue, 
which is visible again in Fig. 2 and partially in Fig. 1. 
Fig. 2 represents a section of another synangium at a level just above 
that of Fig. 4 A. We see that the dimensions have much increased. Two 
of the sporangia have been injured. The walls are thicker than they 
are nearer the apex, and show at least seven layers of cells. The epidermis 
is supported by a hypoderm which is not so regular as is the case at 
a higher level. The lacunar tissue appears at / and l v I have been unable 
to trace any vascular strand at this level. 
Fig. 4 B is a section at a slightly higher level. The septa have given 
way at two places which probably represent the basal parts of the fissures 
shown in Fig. 5 B, which is another section of the same synangium. 
Fig. 4 B shows the hypoderm to consist at this level of an interrupted 
layer of cells empty of contents. In many cases they show scalariform 
marking. This can be best seen in Figs. 1 and 2. They are elongated in 
the long dimension of the sporange, and are probably not continuous with 
the vascular strand but simply hypodermal cells differentiated for some 
special function. It is of course possible they were of use at first as water- 
conducting elements, but it seems more probable that their chief function 
was to secure dehiscence. They may be regarded as physiologically 
analogous with the fibrous layer in the wall of the pollen-sac of Angio- 
sperms. If we refer to Fig. $ hh' we shall see that on the outer wall 
between each sporange there is a group of thin-walled cells which tear 
on dehiscence. This would be brought about by the contraction of the 
convex, free portion of the sporangia! wall. This contraction may very 
well have been due to the hygroscopic structure of the membrane of these 
hypodermal cells. 
At intervals the living parenchyma interrupts these cells. This may 
be seen well in Fig. 3 and in 5 A, at x and x 1 , and it is possible that 
contraction may have been aided by loss of turgidity in these cells. 
The sections taken at a higher level where the sporangia have separated 
from one another are represented in Figs. 3, 5 B, 7 B, and 9. It is easily 
seen that part of the wall of each sporangium is composed of a segment 
of the peripheral wall and a thinner part derived from the partition which 
splits longitudinally, reminding one of the septicidal dehiscence of a syn- 
carpous fruit. There is, however, one exception to this, for the epidermis 
is complete all round the extreme apices which appear to be free primarily, 
M 2 
