1910] MOTTIER—SEX OF ONOCLEA 211 
agin. Rive ota 
sible for the sex of the gametophytes, cultures were made by sowing 
spores thinly upon the soil and keeping the cultures under the most 
favorable conditions available. One such culture may be men- 
tioned in detail. In this 207 spores were sown and 150 prothallia 
harvested. Of these 78 were pure males, while 72 bore archegonia, 
and of the latter 10 per cent were monoecious. Cultures were 
also made to determine, if possible, whether the spores of any 
given sporangium were male or female, as has been reported 
for certain liverworts. In this set of experiments the spores of 
individual sporangia were sown upon earth in separate dishes, with 
results similar to those from spores sown from many sporangia, 
that is, both male and female prothallia were grown; of the female, 
those bearing archegonia, some few were bisexual. Such experi-. 
ments show conclusively that sporangia do not bear spores giving 
rise exclusively to male or female prothallia, and the fact that 
prothallia are bisexual is proof that no sex-differentiating chromo- 
some is present in this fern. 
No effort has been made up to this time by the writer to induce 
the development of antheridia upon “female” prothallia. Inter- 
esting experiments along this line have been carried out by Miss 
Wuist, as mentioned in the foregoing, with the following results: 
monoecious prothallia were obtained by transferring the plants 
from distilled water to Knop’s solution, in which they were further 
cultivated; by transferring “female” prothallia from soil to a 
nutritive solution, and by transferring from one nutritive solution 
to another. 
These experiments indicate that gametophytes bearing arche- 
Sonia only may be induced to develop antheridia as a response to 
environmental conditions. Knowing that dioecism has not been 
completely established, these results, though important, are not 
surprising. They do not show a very far-reaching influence of 
environmental factors in regard to the regulation of the develop- 
ment of sex cells; for I have frequently observed in older cultures, 
that is, about five months after sowing, that certain ‘‘female”’ 
‘Prothallia, in which an egg failed to be fertilized, developed from 
the oldest parts numerous small lobes which give that end of the 
-Prothallium a finely fringed appearance, and upon these lobes 
alge eT hee 
