364 Bower . — The comparative examination of the 
first by anticlinal and later by periclinal walls, the result being 
two, or even three layers, the latter condition showing a 
greater complexity than in the leptosporangiate Ferns ; but 
opposite the point where dehiscence takes place these divisions 
are delayed (x, Fig. 82). Meanwhile the sporogenous cell has 
grown, and divided repeatedly, and formed numerous spore- 
mother-cells, of which the number is much larger than in the 
Polypodiaceae ; their number may be judged from the fact that 
more than twenty appear in a single section (Fig. 82). Each 
of these divides into four, the inner tapetal layer becomes 
glandular and disorganised, the outer however persists for a 
time, but dries up before maturity without becoming glan- 
dular. 
I have already published a preliminary account of the 
origin of the sporangium in Todea barbara x , and am now able 
to give a more full account with figures. This plant shows a 
structure and development of the sporangium which corre- 
sponds in all essential points to that of Osmunda , and there is 
a like irregularity as to the exact position and sequence of the 
segmentations. The essential parts of the sporangium appear 
to originate from a single cell with a square base, and deeply 
sunk in the tissue : having divided by a periclinal wall, the 
outer of the resulting cells undergoes anticlinal divisions (Fig. 
8 3), by which three peripheral cells are cut off from a central 
cell (Figs. 84, 85) : the whole group is still deeply sunk in the 
surrounding tissue, and the young sporangium projects as yet 
but slightly beyond the surface ; it is clear from observation 
from without (Figs. 84, 85) that the disposition of the three 
lateral cells round the central one is similar to that in the 
Polypodiaceae, though the base of the central cell is often 
square. Then follows a periclinal division (Figs. 86, 87), by 
which the archesporium is cut off from a superficial cell : the 
form of the archesporium is variable, sometimes (Fig. 87) it is 
pointed below, and tetrahedral in form, as in the leptosporan- 
giate Ferns ; but this is the less common case : more frequently 
(Fig. 86) it has a square base ; but even when this is so, the 
1 Q. J. M. S. Vol. XXV, p. 1 00, 1885. 
