43 2 Lang. — Studies in the Development and 
what thicker walls with more numerous pits than those 
toward the opposite side of the sporangium. If a section 
of a sporangium at right angles to the line of dehiscence 
be examined, the difference is found to be much more con- 
siderable than appears in surface view. The cells for some 
distance on either side of the line of dehiscence have all their 
walls, especially the inner and vertical, strongly thickened 
(Fig. 1 8). Toward the apex these bands of thick-walled 
cells are broader than near the stalk, and the transition 
from them to the thinner-walled cells of the lateral region 
is more gradual. The latter near the apex have thin outer 
but fairly thick vertical and inner walls, while further from 
the apex the cells become more uniformly thin-walled. 
There are thus bands of thick-walled cells on either side 
of the line of dehiscence, which meet at the apex in the cap 
of isodiametric thick-walled cells, while the rest of the 
epidermal layer is composed of comparatively thin-walled 
cells. The relation of the thin- and thick-walled regions 
of the wall is closely similar to that existing in Atigiopteris 1 . 
The mechanism by which the sporangium opens appears also 
to be essentially the same 2 . When the cells dry up at 
maturity, the thin-walled cells of the lateral region contract 
and pull upon the bands of thick-walled cells, thus widening 
the slit : this in Stangeria is formed by the separation of the 
two rows of cells which compose the line of dehiscence, while 
the cells themselves remain intact. The widely gaping slit, 
which extends from the stalk to the apex, is directed down- 
wards in the natural position of the sporangia. The mature 
sporangium can be induced to open by drying, and closes 
again when moistened. 
Numerous stomata are present in the epidermis of the side 
of the sporangium away from the line of dehiscence and near 
the stalk. Their position is indicated in Fig. 1 7 by dots on 
1 Zeiller, Gites Mineraux, Flore fossile, p. 1 8, Fig. 13. 
2 The mechanism of dehiscence in Angiopteris is described in a paper by Bower, 
read before the Royal Society on May 27, 1897, but not yet published in full. 
I am indebted to Dr. Bower for placing his results and preparations at my disposal 
for purposes of comparison with Stangeria . 
