534 FILICALES 
to be noted that the cells marked (x) do not compose the whole outgrowth, 
but that adjoining cells also contribute in a certain degree, so that 
strictly speaking the whole sporangium is not referable in origin to the 
single cell. The massive stalk is partly formed from surrounding cells: 
this is a further feature for comparison with Eusporangiate types. How 
various the subsequent segmentations may be will be seen from the 
Figs. 296 4, E; these show that the large cell in the centre of the growing 
sporangium: may be of prismatic or of conical form, while they also prove 
% Fic. 296. 
Todea barbara, Mo@re. A=small part of section of pinnule showing two young 
sporangia (x, x). 8, C, D=examples of variety of segmentation, as seen in vertical 
sections. =older sporangia in transverse section, showing differences in sporangia in 
juxtaposition. #=vertical section of sporangium of like age, with square-based sporo- 
genous cell. G=similar sporangium with triangular sporogenous cell. AH, /=vertical 
and transverse sections of older sporangia. The central figures show two unequal 
sporangial stalks, in transverse section, All Xx 200. 
that adjoining cells take part in the formation of the sporangial outgrowth; a 
comparison of Figs. 296 c, D, also brings out clearly the very great difference 
of bulk occasionally seen in sporangia of the same age. The large cell 
in the centre divides usually by three anticlinal walls corresponding to 
those seen in the usual Leptosporangiate type, though the cell which 
remains in the middle may still be either truncate or pointed at the 
base. But sometimes it appears that four lateral cells may be cut off by 
anticlinal walls, as in the largest sporangium in Fig. 296; thus the central 
cell after periclinal divisions in TZodea, may sometimes have the form 
which is characteristic rather of the Eusporangiate sporangia, though this 
is exceptional. Then follows the periclinal division to separate the cap-cell 
from the archesporium: the cell which thus undergoes periclinal division 
