STEIL: SOME NEW CASES OF APOGAMY IN FERNS 99 
of Pieris. Those of Aspidium chrysolobum, A. varium, and A. 
auriculatum become especially large. 
Antheridia are produced on the prothallia of all of the apoga- 
mous species. The antherozoids responded to the chemotactic 
influence of the archegonia of non-apogamous species in all cases in 
which tests were made. The mature antherozoid appears perfectly 
normal and is probably capable of functioning. Ina former note 
(Steil, 1910) it was reported that antheridia had not been observed 
on the prothallia of Pellaea atropurpurea, but in many of my cul- 
tures made since this time they have been formed in large numbers. 
Archegonia have been found on the prothallia of Aspidium 
chrysolobum, but in a large number of the prothallia they are never 
produced (PLATE 4, FIG. 5). The embryo always appears at the 
anterior portion of the cushion and can be readily observed to 
begin its development as a vegetative outgrowth from the pro- 
thallial cells. Over 50 per cent. of the prothallia of Pellaea viridis 
bear archegonia. Whether embryos are produced as a result of 
fertilization in either case has not been determined. In a few 
instances two embryos were observed to develop from a single 
prothallium of P. viridis. One of these was apogamously pro- 
duced, but the other appeared to owe its origin to an egg. Arche- 
gonia were never found.in the prothallia of P. adiantoides, and for 
this reason especial care was exercised in making the cultures of 
P. viridis. Spores were obtained from the New York and the 
Missouri Botanical Gardens and from two plants grown in the 
university greenhouse, but the embryos in all of the cultures made 
from the spores thus obtained were produced apogamously. In 
some of the Pteris cretica varieties archegonia were observed very 
rarely, but an embryo was never found to be developed from an 
ege. 
THE DEVELOPMENT OF THE APOGAMOUS EMBRYO 
The apogamous embryo usually appears as a compact region 
of small cells on the ventral side of the prothallium and posterior 
to the apical notch (PLATE 4, FIGS. 2-5, and PLATE 5, FIGs. 13 
and 20). When the embryo begins its development, the prothal- 
lium has not yet attained its maximum growth. In some species, 
such as Aspidium chrysolobum (PLATE 4, FIGS. I and 2), A. hir- 
