286 Lang.—Development of Cycadean Sporangia . 
projects, forming a very distinct pointed structure (Fig. 12). 
The distinctness of this is due partly to the increase in width 
of the nucellus-apex below the tip, but in part to the further 
growth of the tip itself, as is shown by the assumption of the 
pointed form. The ovule, when this stage of development of 
the nucellus-apex and micropyle has been reached, has an 
embryo-sac of considerable size, in which, however, no distinc¬ 
tion of separate cells is apparent, the prothallus being still 
represented by a layer of cytoplasm with numerous nuclei. 
Little or no destruction of the sporogenous tissue has yet 
taken place. 
No cones have been obtained illustrating the intermediate 
steps between such an ovule and the stage in which the 
embryo-sac has become completely filled with the tissue of 
the prothallus. The latter age is of special interest, since it 
probably is that at which pollination takes place in Stangeria. 
It will therefore be described in some detail, and at the same 
time the course of the vascular bundles in the ovule may be 
traced. The general relation and proportion of parts is shown 
in Fig. 13, which represents a median section of an ovule at 
this stage. In the integument the three layers are distinct, 
though the cell walls of the middle one are still unthickened. 
The long narrow micropylar canal is surrounded by the thick 
margin of the integument which projects as a short beak 
round the external opening. In the apex of the nucellus the 
pollen-chamber has been formed (Figs. 14, 15). The super¬ 
ficial cells of the pointed tip seen in Fig. 12 have their walls 
thickened, and form a very definite boundary to the sides of 
the chamber, suggesting a close comparison with the corre¬ 
sponding region of certain fossil Gymnospermous seeds x . At 
the actual apex of the conical projection, however, the epi¬ 
dermal cells have broken down, thus leaving an opening into 
the cavity formed by the disintegration of the internal tissue. 
From the base of this cavity a strand of more elongated cells 
1 See, for example, Brongniart, Graines Fossiles Silicifiees, PI. Ill, Figs. 8 and 13 
(Cardiocarpus augustodunensis). Renault, Structure comparee de quelques Tiges 
de la Flore Carbonifere, PI. XVII, Figs. 14 and 15 (Cordaianthus Grand' Euryi). 
