II The Ovule of Stangeria paradoxa. 293 
The actual process of fertilization was not observed, the 
youngest fertilized archegonium showing several nuclei in 
its cytoplasm. These were situated in the central area of 
more finely granular protoplasm referred to in the descrip¬ 
tion of the archegonium, and, in the only embryo of this age 
found, were undergoing karyokinetic division. Slightly older 
embryos (Fig. 27) had numerous small nuclei in the cyto¬ 
plasm ; these tended to take up their position at the periphery, 
and were most numerous at the lower end of the embryo. 
In the next stage, though the embryo is still enclosed in the 
wall of the archegonium, it no longer forms a continuous mass 
filling the venter of the latter, but appears as a hollow sac 
enclosing a large cavity (Fig. 28). The occurrence of this 
change has been described by Treub 1 and Ikeno 2 in the 
similar embryo of Cycas ; in this genus also it would appear 
to take place before the embryo has undergone any increase 
in size. As in Cycas, the embryo with its suspensor is devel¬ 
oped entirely from the lower end of the hollow sac of tissue. 
The upper portion remains as a thin layer of cytoplasm with 
free nuclei in it, lining the thin cell-wall, with which the 
embryo surrounds itself. The cells forming the thicker lower 
end of the sac become enclosed by cell-walls, and, as Fig. 29 
shows, become differentiated into the suspensor and embryo. 
The latter has broken through the wall of the archegonium, 
and projects into the tissue of the prothallus. At this stage 
the embryos from the different archegonia of a prothallus, 
though inclined towards one another, are separated by tissue 
of the prothallus. The short suspensor is composed of vacuo¬ 
lated cells; those forming the embryo are meristematic, and 
can be distinguished into an epidermal layer and the internal 
smaller-celled tissue. As the suspensors of the several embryos 
increase in length, the latter come to occupy a single cavity, 
formed by the progressive destruction of the surrounding 
tissue of the prothallus. In the upper part of this common 
space the suspensors, which become considerably coiled and 
folded, are found, while at the base, embedded in the still 
1 Ann. Jard. Bot. Buitenzorg, iv, p. 5. 2 loc. cit. 
