566 FILICALES 
one side, an ill-defined lateral stomium being present, while the rupture 
is by a ragged lateral slit, opened by the straightening annulus (Fig. 316). 
The sorus originates as a smooth upgrowth from the lower surface of the 
pinnule, opposite a nerve, a considerable number of cells being involved 
from the first; no definite mode of segmentation 
has been recognised (Fig. 317 F). As develop- 
ment proceeds, the margin of the upgrowth 
extends all round, as the overarching indusium 
(z, 2); this, undergoing a somewhat regular seg- 
mentation by anticlinal walls, curves so as to 
cover in the sporangia which arise below (s., Fig. 
317 F); the indusium thus precedes the appear- 
ance of the sporangia, as in many other indusiate 
Ferns. The sporangia originate from single cells, 
which have commonly a square base, though it 
from nee! Hatenia Zectintte may be a question whether this is always so. 
eee ie detached. (After The segmentation is by walls inclined to one 
another ; the first wall is usually on the side next 
to the leaf-surface, and meets one of the lateral walls of the parent cell; 
then follow three other inclined walls, and the segments thus produced 
surround a central triangular wedge-shaped cell, from which finally the 
cap-cell is cnt off in the usual way (Fig. 317 £). 
The further segmentation of the central cell follows the course usual 
for Leptosporangiate Ferns; a double tapetum is formed (Fig. 317 D) of 
which the inner cells become greatly enlarged, and their nuclei, clustering 
round the sporogenous group of cells, and undergoing fragmentation, 
present an appearance very like that in Gleichenia; the archesporium 
divides into 16 spore-mother-cells, and the typical number of spores seems 
to be 64; countings of mature spores gave figures between 48 and 64 as 
the produce of single sporangia. Sections of sporangia, when cut so as 
to traverse the annulus throughout its course, show the wall as a single 
layer, but composed of more numerous cells than is the case in many 
of the Leptosporangiate Ferns (Fig. 317 D); this is also brought out 
plainly in views of the mature sporangia from without (Figs. 317 A, B, C). 
It may be noted further that the stalk, which remains very short, is 
rather massive, and consists of a peripheral series of six or seven cells, 
surrounding a central cell (Fig. 317 4), which corresponds to the structure 
of the stalk in the massive sporangia in Gletchenia and Osmunda. 
The mature sporangium is a body of rather irregular and variable 
form, owing apparently to pressures in the developing sorus. The annulus 
is incomplete and variable in position; it consists of a series of large 
cells, 20 or more in number, which takes an oblique and sinuous course, 
corresponding in the main to that in Glecchenia. The sporangia are 
liable to be tilted right or left, as shown in Fig. 317 B, which represents 
two sporangia 7” stfu, as seen from the side facing the indusium. 
Fic. 316. 
