NOTES ON THE SEX OF THE GAMETOPHYTE OF 
ONOCLEA STRUTHIOPTERIS 
Davip M. MoTTIER 
During the past two or three years the writer has been collecting 
data from a study upon the gametophyte of Onoclea Struthi- 
opteris with reference especially to the dioecious character of the 
prothallia, and while this study is in no way completed, it has been 
deemed advisable to make public some of the facts observed, 
inasmuch as the data obtained supplement those set forth in a very 
interesting paper, appearing in a recent number of this journal, by 
Miss WuIsT.* 
The impression is general that the prothallia of Onoclea Struthi- 
opieris are dioecious,? and although this is generally true, it is not 
strictly so, as bisexual prothallia may readily be found under 
ordinary and perhaps optimum cultural conditions. In 1907, in 
an address before the Indiana Academy of Science,’ I made the 
following statement: 
The writer has recently begun the study of a fern, whose prothallia have 
been reported as strictly dioecious, and if the spores of the same are well nour- 
ished, female prothallia will predominate, while with poor nourishment the 
vast majority of spores will give rise to male gametophytes. An examination 
of cultures grown under favorable conditions for laboratory use, in which the 
Spores were sown thickly, showed that certain spores produced strictly male 
plants, others female, and still others bisexual prothallia. A small number of 
Spores were isolated and grown under similar and very favorable conditions, 
with similar results. The pure males were almost equal in number to those 
bearing the female organs, while the bisexual plants were few, being about 
4 per cent of the whole number. The foregoing results seem to lend encour- 
agement to the view that environmental conditions may have much less to do 
with the development of male and female prothallia than had hitherto been 
Supposed. The very brief study showed clearly that in the fern in question 
* Wuist, Exizaneta Dororny, The physiological conditions for the development 
ne Btigeecnee: prothallia in Onoclea Struthiopteris. Bor. GAZETTE 49:216-2109. 
? CampBELL, D. H., Mosses and ferns. Edition 2, p. 314. 1905. 
" . Mortirr, D. M., History and control of sex. Proc. Ind. Acad. Sci. 1907. pp. 
nen 
209] [Botanical Gazette, vol. 50 
