Morphology of Cyc adeem Sporangia . 433 
the wall. Their guard-cells are depressed below the surface, 
and subsidiary cells are present. The stomata do not become 
fully developed until the sporangium is nearly mature. They 
are found in a similar position on microsporangia of Cera to- 
zamia and Encephalartos , the only genera of which mature 
material was at hand for comparison. Stomata are present 
on the ovules and sometimes the pollen-sacs of Angiosperms, 
but, so far as I am aware, not on the sporangia of any Vascular 
Cryptogam. The two sporangia represented in Fig. 17 also 
illustrate the difference in form between the sporangia at 
the outer border of the soriferous region (a) and those situated 
more centrally (b) ; the existence of this difference was referred 
to above, and the figure will explain its nature without further 
description. 
The pollen-grain of Stangeria 1 is at first spherical ; later 
one side becomes infolded, and its shape is oval. At first 
only one nucleus is present (Fig. 16, /), but before the 
pollen is shed each grain contains three cells, the large t 
vegetative cell with its spherical nucleus and two cells with 
thin cell-walls (Fig. 18) ; these are situated against the side 
which becomes infolded. Since only these two cells were 
present in pollen which had been germinated by Dr. Scott, it 
is safe to conclude that they are the only ones cut off in 
the course of development of the pollen of Stangeria . 
Stangeria thus agrees with the other Cycads in the structure 
of its pollen. 
The ovule of Stangeria agrees closely in the later stages 
of development with the Cycads examined by Warming 1 2 and 
Treub 3 . The embryo-sac was already present in the youngest 
material yet obtained ; it is developed from the lowest of 
a row of three cells, which is derived from a single cell 
occupying a central position in the nucellus. The embryo- 
sac, in the ovules of this cone, was but slightly larger than 
1 Braun, loc. cit. p. 315, described the pollen -grain of Stangeria , but did not 
determine the number of basal cells (Basalzellen). 
2 Recherches et remarques sur les Cycadees. Copenhagen, 1877. 
3 Loc. cit. 
