196 BOTANICAL GAZETTE [MARCH 
walls of the cells between the bands, 7.e. those of the line of dehiscence, 
are at first very thin, but thicken up later, until they are almost as 
thick as those of the other cells. 
The apex of the sporangium is composed of isodiametric cells 
(in cross-section) with uniformly thickened walls, beneath which 
is a group of cells which are thickened in the same way (jigs. 34-36). 
From the apex, extending along either side of the line of dehiscence, 
the cells of the bands are longer, narrower, and have the inner and 
vertical walls thickened, the bands extending along the crest from 
the apex almost to the base of the sporangium. 
The mature condition of the sporangium of Encephalartos, the 
only stage of this genus available, is much the same (fig. 35). 
The older stages of the sporangium of Ceratozamia show the apical 
group of cells (jig. 31) projecting only slightly; and the band cells 
are little more thickened than the other cells of the sporangium, but 
are narrower. Cross-sections made from the younger stages (fig. 37) 
show in the wall a double line of cells running from the outside into 
the sporangial cavity, whose contents stain more deeply. These 
lie just beneath the line of dehiscence, and are therefore like a plate 
cutting into the wall from the surface. Just under the line of de- 
hiscence in Marattia there are deeply colored mucilaginous cells 
which may aid in dehiscence; these slightly resemble those in Cerato- 
zamia. Older stages of the wall do not show this plate; but there are 
occasionally several cells under the line of dehiscence, in which there is 
a great number of crystals. These are even more striking in Zamia, 
where early stages in their formation have not been seen (jig. 38). 
At the time of spore-formation in Zamia there is also just opposite 
the cells of dehiscence, on the inner surface of the sporangium, a 
projection into the wall of the inner layers and of the tapetum (fig. 
38). The cells between are flattened and out of shape, as if degenera- 
tion had begun. This has been seen in a number of sections, and 
may or may not be a normal occurrence. Enough sections have 
not been seen to make a definite statement as to the function of 
these cells, but it may be suggested that there is a breaking down of 
the walls at the time of dehiscence, which aids in the breaking open 
of the sporangium. This may be seen in Danaea, where of course 
there is no mechanical arrangement for dehiscence; and possibly 
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