100 STEIL: SOME NEW CASES OF APOGAMY IN FERNS 
‘ tipes and A. auriculatum, the prothallia increase considerably in 
size as the young embryo is developing. In most instances the 
cushion has not been formed when the embryo makes its appear- 
ance. The embryo proceeds in development with the growth of 
the cushion. On account of the early appearance of the embryo. 
it was easy to determine when apogamy occurred in any species, 
While the embryo usually occurs back of the apical region 
its position varies in the different species and even in the same 
species. In some cases the embryo is developed directly in the 
apical notch (PLATE 5, FIGS. 14. and 15). A cylindrical or conical 
process produced as an outgrowth of the apical region may bear 
on some portion of it the apogamous embryo. Sometimes the 
embryo may be produced at a considerable distance posterior to the 
notch (PLATE 5, FIGS. 13 and 20). In still other instances the 
embryo is formed on the lobes of the prothallium (PLATE 5, FIG. 
19). From the foregoing, it is seen that the apogamous embryo 
can be produced on portions of the prothallia where archegonia 
have never been observed to be formed in any non-apogamous 
species. 
Tracheids are visible among the prothallial cells of some of the 
apogamous species long before the prothallium has reached its 
maximum growth (PLATE 4, FIG. 3, and PLATE 5, FIG. 20). 
It is usually in the portion of the prothallium where the 
tracheids appear that the apogamous embryo begins its develop- 
ment. The tracheids are readily observed in many cases, since 
the prothallium frequently becomes pale in the region of the notch 
and where these elements are produced. The cells in this portion 
of the prothallium contain fewer chloroplasts than the neighboring 
prothallial cells (PLATE 5, FIG. 20). In the species of Pteris the tra- 
cheids are most frequently observed (PLATE 4, FIGS. 3, 4, and 6). 
In many instances the light area extends forward as a cylindrical 
or conical process, already mentioned (PLATE 4, FIG. 6). 
The embryo is usually surrounded by hairs, each composed ’of 
a single row of cells (PLATE 5, FIG. 13). In some species, as in 
Aspidium chrysolobum and A. Tsus-Simense, scales are also pro- 
duced. 
In only a few species has the development of the apogamous 
embryo been studied in sections. It seems that the apical cell of 
