1910] HOYT—FERTILIZATION IN FERNS 347 
fern spores, however, because more than 100 young sporophytes from 
the different pots were obtained and raised to a distinguishable age, 
and all were of the species which was planted in the pot from which 
they came. 
In order to prevent the occurrence of fertilizations in the pots, 
all cultures were watered very sparingly and only from below—by 
pouring water into the saucers. The soil and air were kept just 
moist enough to keep the prothalli in good condition. The soil was 
not allowed to become wet and no water was allowed to collect on 
the glass. In spite of these precautions, many fertilizations took 
place in some of the pots. Except in one case noted, however, no 
culture was used for archegonia unless it was free from sporelings 
for at least a week before and two weeks after the experiment. 
In most cases the prothalli used for archegonia were examined 
under the microscope before being placed in water, and any portions 
of the prothalli bearing antheridia were cut off, and all adherent male 
prothalli were removed. In some cases the prothalli were not exam- 
ined dry, but were placed directly in water. Antheridia or male 
prothalli, if present, were removed before escape of the sperms had 
occurred. All such cases were recorded, and no female prothallus 
was used for crossing if there was any reason to believe that sperms of 
its own species were present. By these means it was possible to be 
fairly sure that no antheridia of the species to be used as female 
were present; sometimes, however, antheridia were overlooked. In 
cases where the prothalli were fixed, therefore, the entire prothallus 
Was sectioned and every section was examined for antheridia. Over 
150 prothalli were thus sectioned and examined, and among these, 
antheridia were found in only two cases where they had not been 
detected by the previous examination. This method, therefore, 
seems to'be a satisfactory one. 
From the fact that the above methods were carrried out faithfully, 
the conclusion seems warranted that, in this work, we are dealing 
with sperms and eggs of known parentage. 
3. RESULTS 
Abundant entrance of sperms has occurred into archegonia of the 
Same species and of different species. When the sperm and egg were 
