STEIL: SOME NEW CASES OF APOGAMY IN FERNS 95 
in the university greenhouse, but the prothallia never showed any 
peculiarities in their development, and embryos were never pro- 
duced by fertilization. Hence it appears that cultural conditions 
were not a factor in inducing apogamy in any case. 
In the majority of cases, the prothallia were grown until em- 
bryos were formed, either as a result of fertilization or apoga- 
mously. Parthenogenesis was not excluded in the non-apoga- 
mous species. To determine this point a cytological investigation 
would have been necessary. 
The conclusions are in no case based on a single culture but on 
a large number of cultures. Cultures in which only a few pro- 
‘thallia were obtained were always discarded. Great care was 
exercised in handling the spores before sowing in order to avoid, 
so far as possible, mixing those of different species. 
Two sets of cultures were made of each of the ferns tested for 
apogamy. In one set only a small number of spores were sown 
to avoid crowding the prothallia. The prothallia under these con-. 
ditions grew to a good size and became heart-shaped. It was be- 
lieved that these cultures were favorable for the development of 
archegonia. The other cultures were made by sowing a large 
number of spores. The majority of the prothallia in these cul- 
tures were irregular in form and usually produced numerous an- 
theridia. If embryos were produced, they appeared in both types 
of cultures. From the two sets of cultures it was possible to 
determine whether sex organs developed. 
While the prothallia of the different species were growing, they 
were carefully examined from time to time with a microscope. 
Since in a number of species investigated tracheids appeared 
among the prothallial cells, it was not difficult to determine the 
apogamous forms. In all the apogamous species a region com- 
posed of small cells made its appearance posterior to the apical 
notch. In every instance when such an area of small cells ap- 
peared on the surface of the prothallium, the embryo proved to 
be of apogamous origin. When archegonia were produced in any 
of the apogamous species, they were absent on many of the pro- 
thallia. These, however, always produced embryos apogamously. 
In some species longitudinal sections of the prothallia were made 
in order to determine with more certainty the origin of the embryo. 
