212 BOTANICAL GAZETTE [SEPTEMBER 
numerous antheridia were produced. Such prothallia were well 
nourished, with a deep-green color, and continued to develop the 
archegonial meristem, which produced continuously numerous 
archegonia. The specimens before me at this writing are 5-6 mm. 
in length. As stated, the antheridial lobes were confined generally 
to the posterior or older parts of the prothallia, but they may 
extend a short distance forward along the margins. Antheridia 
were not observed, except in very rare cases, upon the archegonial 
meristem. 
After all, the fact that archegonial plants may develop organs 
of the opposite sex, either normally or in response to conditions 
controlled in a measure by the experimenter, may readily find a 
satisfactory explanation, but the case may be different in regard to 
the prothallium that produces only antheridia. If purely male 
prothallia of Onoclea Siruthiopteris are merely those that do not 
become large enough, because of nourishment, to bear archegonia, 
why is it that these pure males cannot be made to grow large enough 
to develop the female organ? The writer knows of no case on 
record in which this has been done. If the male plants could be 
made to develop the archegonial meristem and its archegonia, 
then it may be said that the environment (which of coures means 
chiefly nutrition) controls sex to that degree. The writer has not 
been able to believe that male prothallia of the fern in question 
are merely those that do not become large enough to bear arche- 
gonia, but that certain spores are predetermined to develop into 
purely antheridial plants, and others into those capable of form- 
ing archegonia. If there were a sex-determining chromosome, — 
then one half of the spores would be male and one half female, 
but as the ‘“‘female” prothallia bear occasionally antheridia, It 
cannot be said that a sex-determining chromosome is present. [he 
explanation which we are able to give at present is that in certai 
spores the male tendency is dominant, while in others it is the 
female, but such statements mean little at present. ? 
In a foregoing paragraph reference was made to the mortality 
among the spores, and to the variation in their size and apparent 
vigor. Some are larger and more healthy looking than others, and, 
as in many plants, many spores seem to be and doubtless are 
